Vitamin D

What is it?

Vitamin D is required for the regulation of the minerals calcium and phosphorus found in the body. It also plays an important role in maintaining proper bone structure.

Sun exposure is an easy, reliable way for most people to get vitamin D. Exposure of the hands, face, arms, and legs to sunlight 2-3 times a week for about one-fourth of the time it would take to develop a mild sunburn will cause the skin to produce enough vitamin D. The necessary exposure time varies with age, skin type, season, time of day, etc. Just 6 days of casual sunlight exposure without sunscreen can make up for 49 days of no sunlight exposure. Body fat acts like a kind of storage battery for vitamin D. During periods of sunlight, vitamin D is stored in fat and then released when sunlight is gone.

Vitamin D deficiency is more common than you might expect. People who don't get enough sun, especially people living in Canada and the northern half of the US, are especially at risk. However, even people living in sunny climates might be at risk, possibly because people are staying indoors more, covering up when outside, or using sunscreens to reduce skin cancer risk.

Older people are also at risk for vitamin D deficiency. They are less likely to spend time in the sun, have fewer "receptors" in their skin that convert sunlight to vitamin D, may not get vitamin D in their diet, may have trouble absorbing vitamin D even if they do get it in their diet, and may have more trouble converting dietary vitamin D to a useful form due to kidney problems. In fact, some scientists suggest that the risk for vitamin D deficiency in people over 65 years of age is very high. As many as 40% of older people living in sunny climates such as South Florida might not have optimal amounts of vitamin D in their systems.

Vitamin D supplements may be necessary for older people, people living in northern latitudes, and for dark-skinned people who need extra time in the sun, but don't get it. Talk to your health care provider about whether a supplement is best for you.

Coronavirus disease 2019 (COVID-19): Some experts suggest taking 400-1000 IU (10-25 mcg) of vitamin D daily to reduce the risk for COVID-19. While these doses of vitamin D are likely safe, there is no good data to support the use of vitamin D for COVID-19. If you opt to take vitamin D for COVID-19, be sure to follow healthy lifestyle choices and proven prevention methods as well.

Is it Effective?

Natural Medicines rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.

The Effectiveness ratings for Vitamin D are as follows:Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.

The effectiveness ratings for are as follows:

A rare, inherited bone disorder marked by low levels of phosphate in the blood (familial hypophosphatemia). Taking vitamin D in forms known as calcitriol or dihydrotachysterol by mouth along with phosphate supplements is effective for treating bone disorders in people with low levels of phosphate in the blood.
Underactive parathyroid (hypoparathyroidism). Low levels of parathyroid hormone can cause calcium levels to become too low. Taking vitamin D in forms known as dihydrotachysterol, calcitriol, or ergocalciferol by mouth is effective for increasing calcium blood levels in people with low parathyroid hormone levels.
Softening of the bones (osteomalacia). Taking vitamin D3 is effective for treating softening of the bones. Also, taking vitamin D in a form known as calcifediol is effective for treating softening of the bones due to liver disease. In addition, taking vitamin D2 is effective for treating softening of the bones caused by medications or poor absorption syndromes.
A bone disorder that occurs in people with kidney disease (renal osteodystrophy). Taking vitamin D in a form known as calcitriol by mouth manages low calcium levels and prevents bone loss in people with kidney failure.
Rickets. Vitamin D is effective for preventing and treating rickets. A specific form of vitamin D, calcitriol, should be used in people with kidney failure.
Vitamin D deficiency. Vitamin D is effective for preventing and treating vitamin D deficiency. Vitamin D also improves symptoms that result from vitamin D deficiency. Taking vitamin D2 by mouth or administering it as a shot into the muscle seems to help treat a muscle disease associated with vitamin D deficiency.

Likely Effective for...

Bone loss in people taking drugs called corticosteroids. Taking vitamin D by mouth prevents bone loss in people taking drugs called corticosteroids. Also, taking vitamin D alone or with calcium seems to improve bone density in people with existing bone loss caused by using corticosteroids.
Weak and brittle bones (osteoporosis). Taking vitamin D3 along with calcium seems to help prevent bone loss and bone breaks.
Psoriasis. Applying vitamin D in the form of calcitriol, calcipotriene, maxacalcitol, or paricalcitol can help treat plaque-type psoriasis. Applying vitamin D along with corticosteroids seems to work better than applying vitamin D or corticosteroids alone. But taking vitamin D by mouth does not seem to improve psoriasis.

Possibly Effective for...

Cavities. Clinical research suggests that taking vitamin D2 or D3 reduces the risk of cavities by 36% to 49% in infants, children, and adolescents. Also, exposure to more vitamin D before birth might reduce the risk of having decayed teeth at 12 months of age. But it is unclear if taking vitamin D supplements during pregnancy reduces the risk of decayed teeth in the child.
Heart failure. Some early research suggests that people with low vitamin D levels have an increased risk of developing heart failure compared to those with higher vitamin D levels. Some research shows that taking vitamin D supplements can help reduce the risk of developing heart failure in some women. Also, most research suggests that taking vitamin D supplements may decrease the risk of death in people with heart failure.
Bone loss in people with overactive parathyroid (hyperparathyroidism-related bone loss). Taking vitamin D3 by mouth seems to reduce parathyroid hormone levels and bone loss in women with a condition called hyperparathyroidism.
Infection of the airways. Most research shows that taking vitamin D helps prevent respiratory infections in children and adults. A respiratory infection can be the flu, a cold, or an asthma attack triggered by a cold or other infection. Some research shows that taking vitamin D during pregnancy reduces the risk of these infections in the child after birth. But conflicting results exist.
Preventing tooth loss (tooth retention). Taking calcium and vitamin D3 by mouth appears to prevent tooth loss in elderly people.

Possibly Ineffective for...

Heart disease. People with low blood levels of vitamin D seem to have a greater chance of developing heart disease. But taking a vitamin D supplement does not seem to prevent heart disease, heart attack, stroke, or other serious heart-related events in most people. While some evidence suggests vitamin D might help prevent heart disease in elderly people, higher-quality research is still needed to confirm.
Coronavirus disease 2019 (COVID-19). There is no evidence suggesting that taking vitamin D will help to prevent or treat COVID-19. Although some studies have found that low vitamin D levels might be linked with a higher risk for COVID-19, this link is not confirmed when results of available studies are combined. Also, giving high-dose vitamin D to patients in the hospital with COVID-19 doesn't seem to improve survival or reduce symptoms.
Critical illness (trauma). The most reliable research shows that giving vitamin D to people with low vitamin D levels who are in the hospital with a critical illness does not make them more likely to live.
Fractures. Vitamin D doesn't seem to prevent fractures in older people who do NOT have osteoporosis when it is used alone or in low doses with calcium. Taking higher doses of vitamin D along with calcium might prevent fractures in some older people who do NOT have osteoporosis. But this combination is unlikely to help most people.
High blood pressure. Taking vitamin D doesn't seem to lower blood pressure in most people with high blood pressure. But it might be beneficial in people with high blood pressure and very low blood levels of vitamin D.
Prostate cancer. Taking vitamin D doesn't seem to reduce cancer progression or death from prostate cancer.
Tuberculosis. Most research shows that taking vitamin D does not help to cure tuberculosis or make it less severe. Taking vitamin D also does not seem to reduce the risk of a child catching tuberculosis.

Insufficient Evidence to Rate Effectiveness for...

Hay fever. Early research in people who have hay fever and vitamin D deficiency shows that taking vitamin D once weekly for 8 weeks can reduce symptoms of hay fever.
Alzheimer disease. People with Alzheimer disease seem to have lower blood levels of vitamin D than people without Alzheimer disease. But vitamin D deficiency doesn't seem to be linked with an increased risk of developing Alzheimer disease.
Asthma. People with asthma and low blood levels of vitamin D seem to need to use an inhaler more often and have a higher risk of asthma complications. However, it's not clear if vitamin D supplements can help. Some research shows that taking vitamin D by mouth for up to one year can reduce the rate of severe asthma attacks in adults and children with asthma. But it's still too soon to know which, if any, people with asthma are most likely to respond to treatment with vitamin D. There is also interest in taking vitamin D during pregnancy to reduce the risk of a child developing asthma or wheeze. While some research found that this can reduce the risk in children at 3 years of age, this benefit seems to disappear by the time a child reaches 6 years of age.
Athletic performance. Vitamin D does not seem to improve exercise performance in athletes. But studies have been small and short-term, so more research is needed to confirm.
Eczema (atopic dermatitis). Early research shows that taking vitamin D supplements during pregnancy does not reduce the risk of a child developing eczema during the first 3 years of life.
Irregular heartbeat (atrial fibrillation). Early research found a link between taking vitamin D and reduced incidence of irregular heartbeat in women after menopause.
Attention deficit-hyperactivity disorder (ADHD). Early research shows that taking vitamin D in addition to standard treatment might improve evening symptoms of ADHD, but vitamin D does not seem to affect morning symptoms, hyperactivity, and trouble paying attention in children with ADHD.
Autism. Vitamin D seems to improve symptoms such as irritability and hyperactivity in children with autism.
Overgrowth of bacteria in the vagina. Early research suggests that taking vitamin D does not prevent bacterial vaginosis in women at high risk for sexually transmitted disease when taken along with standard therapy.
Breast cancer. Evidence on the effects of vitamin D on breast cancer risk is not clear. Some evidence suggests that taking vitamin D supplements might reduce the risk of breast cancer in women who are not yet in menopause but not in women who are already in menopause. However, it is possible that higher doses of vitamin D might provide benefit, More research is needed to understand whether vitamin D is helpful for preventing breast cancer.
A lung disease that affects newborns (bronchopulmonary dysplasia). Early research suggests that low vitamin D levels are linked to a greater risk for this lung disease.
Cancer. Taking vitamin D doesn't seem to help prevent cancer. It's unclear if taking vitamin D benefits people already diagnosed with cancer. Some research shows it might help prevent cancer from spreading and help people with cancer live longer. But not all research agrees. More research is needed to determine which people with cancer, if any, are most likely to benefit from vitamin D.
Child growth. Early research shows that taking vitamin D while pregnant does not seem to increase infant growth.
Long-term kidney disease (chronic kidney disease or CKD). Research suggests that vitamin D decreases parathyroid hormone levels in people with chronic kidney disease. However, taking vitamin D does not appear to lower the risk of death or heart problems in people with kidney disease. Also taking vitamin D might increase calcium and phosphate levels in people with kidney disease.
A lung disease that makes it harder to breathe (chronic obstructive pulmonary disease or COPD). People with COPD seem to have lower vitamin D levels that people without COPD. Taking a vitamin D supplement does not seem to decrease symptoms of COPD.
Memory and thinking skills (cognitive function). Early research shows low vitamin D levels are linked to worse mental performance compared to high vitamin D levels. However, it's not clear if taking vitamin D can improve mental function.
Colon cancer, rectal cancer. While conflicting evidence exists, most research shows that taking vitamin D doesn't help prevent colorectal cancer. It's unclear if vitamin D benefits people already diagnosed with colorectal cancer. Some research shows that taking vitamin D doesn't improve survival or prevent relapse in people with colorectal cancer. But other research shows that taking high doses of vitamin D daily might make people with advanced colorectal cancer less likely to experience disease progression or death. More research is needed to confirm.
Diseases, such as Alzheimer disease, that interfere with thinking (dementia). Early research suggests that people with dementia have lower blood levels of vitamin D than people without dementia. But it's not known if vitamin D supplements are helpful in people with dementia.
Depression. Vitamin D does not seem to prevent depression. Also, early research shows that taking vitamin D doesn't improve the symptoms of depression for most people. But people with low vitamin D levels or very severe symptoms of depression may benefit from taking vitamin D.
Diabetes. Some research shows that people with lower vitamin D levels may be more likely to develop type 2 diabetes compared to people with higher vitamin D levels. But taking vitamin D does not seem to prevent the development of diabetes from in people with normal vitamin D levels and prediabetes. It is unclear if taking vitamin D supplements can treat type 2 diabetes. Results from research are conflicting. Early research suggests that giving vitamin D supplements to infants daily during the first year of life is linked to a lower risk of developing type 1 diabetes later in life. Finally, some research shows that taking vitamin D decreases the risk of diabetes during pregnancy.
Kidney damage in people with diabetes (diabetic nephropathy). In people with diabetic nephropathy, vitamin D seems to reduce protein in the urine and reduce inflammation. However, vitamin D does not seem to improve certain markers of kidney function.
Menstrual cramps (dysmenorrhea). High dose vitamin D might reduce pain in adolescents with menstrual cramps.
Fall prevention. The role of vitamin D for fall prevention is confusing and controversial. Clinical practice guidelines published in 2010 recommend that elderly people who have low levels of vitamin D or who are at an increased risk of falling take 800 IU of vitamin D per day to reduce the risk of falling. These recommendations are supported by both population research and some clinical studies. People who do not have enough vitamin D tend to fall more often than people who do. Some research shows that taking vitamin D reduces the risk of falling and the rates of falls in elderly people. It's not known if vitamin D works better when taken alone or with calcium. There is also some speculation that vitamin D only reduces falls in people who are vitamin D deficient. Despite these positive findings, some research shows that vitamin D doesn't prevent falls in elderly people. The best evidence to date shows that vitamin D does not reduce the risk of falling in elderly people. Current clinical practice guidelines do not recommend vitamin D for fall prevention in older adults who live at home and do not have osteoporosis or low vitamin D levels. There is some belief that the conflicting results regarding the effects of vitamin D on fall prevention result from the way in which clinical trial data is reported. Also, the size of the clinical trial may affect the results. It is possible that some patients may still benefit from vitamin D supplementation for reducing fall risk. But who exactly might benefit and what dose or duration of treatment is optimal, if any, remains unclear. For those who are at risk for vitamin D deficiency, a vitamin D supplement should still be considered.
Fibromyalgia. Early research suggests that taking vitamin D might decrease pain in people with fibromyalgia and low vitamin D levels in the blood. But taking vitamin D does not seem to help mood or quality of life.
A type of persistent anxiety marked by exaggerated worry and tension (generalized anxiety disorder or GAD). Early research shows that adding vitamin D to regular treatment seems to help reduce anxiety in people with this condition.
Stem cell transplant. Early research in people who have had a stem cell transplant shows that taking calcitriol, the active form of vitamin D, might help the immune system to recover faster.
Swelling (inflammation) of the liver caused by the hepatitis C virus (hepatitis C). Early research suggests that adding vitamin D to regular treatment for hepatitis C helps to eliminate the hepatitis C virus.
High levels of cholesterol or other fats (lipids) in the blood (hyperlipidemia). People with lower vitamin D levels seem to be more likely to have high cholesterol than people with higher vitamin D levels. Limited research shows that taking calcium plus vitamin D daily, in combination with a low-calorie diet, significantly raises "good"(HDL) cholesterol and lowers "bad"(LDL) cholesterol in overweight women. However, taking calcium plus vitamin D without dietary restrictions does not reduce LDL cholesterol levels. Other research suggests that vitamin D might actually increase LDL and have no beneficial effect on HDL, triglycerides, or total cholesterol.
Bone loss in people with kidney transplants. Early research shows that taking vitamin D in a form known as calcitriol along with calcium does not decrease bone loss in people with kidney transplants.
Prediabetes. Low levels of vitamin D have been linked to a higher chance of prediabetes. Taking vitamin D might slow the development of diabetes in people with low vitamin D levels. But it doesn't seem to help in people with prediabetes who have normal vitamin D levels.
Infant development. Early research shows that taking vitamin D while pregnant does not seem to improve memory and thinking skills in the child. However, infants and children exposed to higher levels of vitamin D during pregnancy might have slightly better memory and thinking skills.
Long-term swelling (inflammation) in the digestive tract (inflammatory bowel disease or IBD). Vitamin D seems to reduce the chance of relapse in people with IBD
Infants born weighing less than 2500 grams (5 pounds, 8 ounces). The effect of taking vitamin D during pregnancy on the risk of low birth weight or small gestational age birth is inconsistent. Additional studies are needed to determine who might benefit, if any, and what dose or formulation of vitamin D is optimal to prevent low weight at birth.
A grouping of symptoms that increase the risk of diabetes, heart disease, and stroke (metabolic syndrome). There is conflicting evidence about the link between vitamin D and metabolic syndrome. Some research found that higher vitamin D levels are linked to a lower risk of metabolic syndrome. While other research has found that women 45 years and older who consume high amounts of vitamin D or take vitamin D supplements do not have a lower risk of developing metabolic syndrome. Adults with metabolic syndrome taking vitamin D supplements also do not seem to experience an improvement in metabolic measures.
Multiple sclerosis (MS). Early research shows that taking vitamin D long-term can reduce the risk of developing MS in women by up to 40%. Taking at least 400 IU daily, the amount typically found in a multivitamin supplement, seems to work the best. However, vitamin D does not seem to reduce the risk of relapses in people that already have MS.
Muscle strength. Taking vitamin D doesn't appear to improve muscle strength in people with normal vitamin D levels. But taking vitamin D by mouth, alone or in combination with calcium, may improve hip and leg muscle strength in people who have low levels of vitamin D. In the elderly with low levels of vitamin D, vitamin D seems to be helpful when taken with calcium.
A group of cancers in which the body can't make enough healthy blood cells (myelodysplastic syndromes). Taking vitamin D in forms known as calcitriol or calcifediol by mouth seems to help people with myelodysplastic syndrome.
Nonmelanoma skin cancer. Taking vitamin D doesn't seem to prevent nonmelanoma skin cancer in patients with colorectal cancer.
Obesity. Early research shows that people with lower vitamin D levels are more likely to be obese than those with higher levels. Women taking calcium plus vitamin D are more likely to lose weight and maintain their weight. But this benefit is mainly in women who did not consume enough calcium before they started taking supplements. Other research shows that taking vitamin D helps with weight loss only when blood levels are increased in postmenopausal overweight or obese women. When vitamin D is taken by people who are overweight and normal weight, it does not seem to help with weight loss or fat loss.
Osteoarthritis. Research about the effects of vitamin D on osteoarthritis is conflicting. It is possible that higher doses of vitamin D reduce pain in osteoarthritis, while lower doses do not.
Ear infection (otitis media). The effect of vitamin D status on ear infections is unclear. Early research found that ear infections seem to be linked to lower levels of vitamin D in the blood. However, lower vitamin D levels are not linked to a higher risk of ear infections.
Death from any cause. Although taking vitamin D alone does not seem to be beneficial, taking vitamin D with calcium might modestly reduce the risk of death from any cause.
Pain. Early research shows that taking vitamin D might reduce pain in people with long-term pain. More research is needed to confirm these results.
Parkinson disease. Low levels of vitamin D have been linked to increased risk of Parkinson disease. Higher levels of vitamin D have been linked to milder symptoms of Parkinson disease. But taking vitamin D supplements doesn't seem to improve Parkinson disease symptoms, although it might help prevent the disease from worsening. More studies are needed.
A serious gum infection (periodontitis). Early research shows that higher blood levels of vitamin D are linked with a reduced risk of gum disease in people 50 years of age or older. However, this does not seem to be true for adults younger than 50 years. It is not known if taking vitamin D supplements reduces the risk of gum disease.
Pneumonia. People with vitamin D deficiency might have a higher risk for developing pneumonia. But limited research in children shows that taking one large dose of vitamin D doesn't prevent pneumonia or make it less severe.
A hormonal disorder that causes enlarged ovaries with cysts (polycystic ovary syndrome or PCOS). Early research shows that taking vitamin D might improve ovulation in women with PCOS. Vitamin D taken together with metformin might also make menstrual cycles more regular. But taking vitamin D alone doesn't seem to help regulate menstrual cycles. Women with PCOS who have normal levels of vitamin D seem to have better pregnancy rates than women with PCOS and low levels of vitamin D. But it's unclear if taking a vitamin D supplement can improve pregnancy rates in women with PCOS.
A pregnancy complication marked by high blood pressure and protein in the urine (pre-eclampsia). Some research shows that taking vitamin D might prevent pre-eclampsia.
High blood pressure during pregnancy. Taking vitamin D doesn't seem to high blood pressure during pregnancy.
Premenstrual syndrome (PMS). Some early research suggests that consuming more vitamin D from the diet might help to prevent PMS or reduce symptoms. Taking vitamin D supplements does not seem to prevent PMS. However, taking vitamin D plus calcium might reduce PMS symptoms.
Preterm birth. Low levels of vitamin D in pregnant women have been linked with an increased risk of preterm birth. But it's unclear if taking vitamin D supplements can prevent preterm birth.
Rheumatoid arthritis (RA). Early research suggests that older women who consume more vitamin D from foods or supplements have a lower risk of developing RA. However taking vitamin D does not seem to improve pain or RA flares.
Seasonal depression (seasonal affective disorder or SAD). Early research suggests that taking a large dose of vitamin D2 improves symptoms of seasonal depression.
Non-cancerous wart-like growths on the skin (seborrheic keratosis). Early research suggests that applying vitamin D3 to the skin might reduce tumor size in some people with seborrheic keratosis.
Sexual problems that prevent satisfaction during sexual activity. Receiving an injection of vitamin D into the muscle seems to improve sexual problems in women with low levels of vitamin D.
Sickle cell disease. Taking high dose vitamin D seems to reduce pain and improve quality of life in children with sickle cell disease.
Muscle pain caused by statin drugs (statin-induced myalgia). Some reports suggest that taking vitamin D supplements can decrease symptoms of muscle pain in people taking statin drugs. But higher quality research is needed to confirm these results.
Stroke. People with low levels of vitamin D in their blood appear to be more likely to develop stroke than people with higher vitamin D levels. Some research has also found that eating a diet high in vitamin D is linked with a lower risk of stroke. But taking vitamin D supplements doesn't seem to reduce the risk of stroke.
An autoimmune disease that causes widespread swelling (systemic lupus erythematosus or SLE). People with SLE seem to be more likely to have low vitamin D levels. Some early research shows that taking vitamin D supplements might decrease disease activity in people with SLE.
Thinning of vaginal tissue (vaginal atrophy). Early research shows that taking vitamin D supplements for at least one year improves the surface of the vaginal wall. But it doesn't seem to improve symptoms of vaginal atrophy. In women who have this condition from taking a cancer drug called tamoxifen, vitamin D suppositories seem to help improve symptoms.
Dizziness (vertigo).
A skin disorder that causes white patches to develop on the skin (vitiligo).
Swelling (inflammation) of the main airways in the lung (bronchitis).
Warts.
Other conditions.

More evidence is needed to rate vitamin D for these uses.

How does it work?

Vitamin D is required for the regulation of the minerals calcium and phosphorus found in the body. It also plays an important role in maintaining proper bone structure.

Are there safety concerns?

When taken by mouth: Vitamin D is LIKELY SAFE when taken by mouth in recommended amounts. Most people do not commonly experience side effects with vitamin D, unless too much is taken. Some side effects of taking too much vitamin D include weakness, fatigue, sleepiness, headache, loss of appetite, dry mouth, metallic taste, nausea, vomiting, and others. Taking vitamin D for long periods of time in doses higher than 4000 units (100 mcg) daily is POSSIBLY UNSAFE and may cause very high levels of calcium in the blood. However, much higher doses are often needed for the short-term treatment of vitamin D deficiency. This type of treatment should be done under the supervision of a healthcare provider.

When given as a shot: Vitamin D is LIKELY SAFE when given as a shot into the muscle in recommended amounts. Most people do not commonly experience side effects with vitamin D, unless too much is taken. Some side effects of taking too much vitamin D include weakness, fatigue, sleepiness, headache, loss of appetite, dry mouth, metallic taste, nausea, vomiting, and others.

Special Precautions & Warnings:

Pregnancy and breast-feeding: Vitamin D is LIKELY SAFE during pregnancy and breast-feeding when used in daily amounts below 4000 units (100 mcg). Do not use higher doses unless instructed by your healthcare provider. Vitamin D is POSSIBLY UNSAFE when used in higher amounts during pregnancy or while breast-feeding. Using higher doses might cause serious harm to the infant.

Children: Vitamin D is LIKELY SAFE in children when taken by mouth in recommended amounts. But it is POSSIBLY UNSAFE to take vitamin D in higher doses, long-term. Infants from 0-6 months should not take more than 1000 IU (25 mcg) daily. Infants aged 6-12 months should not take more than 1500 IU (37.5 mcg) daily. Children aged 1-3 years should not take more than 2500 IU (62.5 mcg) daily. Children aged 4-8 years should not take more than 3000 IU (75 mcg) daily. Children aged 9 years and older should not take more than 4000 IU (100 mcg) daily.

Hardening of the arteries (atherosclerosis): Taking vitamin D could make this condition worse, especially in people with kidney disease.

A type of fungal infection called histoplasmosis: Vitamin D may increase calcium levels in people with histoplasmosis. This could lead to kidney stones and other problems. Use vitamin D cautiously.

High levels of calcium in the blood: Taking vitamin D could make this condition worse.

Over-active parathyroid gland (hyperparathyroidism): Vitamin D may increase calcium levels in people with hyperparathyroidism. Use vitamin D cautiously.

Lymphoma: Vitamin D may increase calcium levels in people with lymphoma. This could lead to kidney stones and other problems. Use vitamin D cautiously.

Kidney disease: Vitamin D may increase calcium levels and increase the risk of "hardening of the arteries" in people with serious kidney disease. This must be balanced with the need to prevent renal osteodystrophy, a bone disease that occurs when the kidneys fail to maintain the proper levels of calcium and phosphorus in the blood. Calcium levels should be monitored carefully in people with kidney disease.

A disease that causes swelling (inflammation) in body organs, usually the lungs or lymph nodes (sarcoidosis): Vitamin D may increase calcium levels in people with sarcoidosis. This could lead to kidney stones and other problems. Use vitamin D cautiously.

Tuberculosis: Vitamin D might increase calcium levels in people with tuberculosis. This might result in complications such as kidney stones.