High Dose Vitamin D – Are 5,000 IUs of Vitamin D Too Much?

The Vitamin D Council advises that most healthy people can receive 5,000-10,000 IU of vitamin D3 a day without harm. But high dose vitamin D must be accompanied by sufficient calcium and magnesium…and people with certain diseases should only take supplements under the supervision of a knowledgeable doctor. Vitamin D is essential for the absorption of calcium and the prevention of osteoporosis. Recent studies have shown that it may also boost the immune system and help to prevent cancer.

Our body will automatically regulate how much vitamin D it produces from sunshine. Studies show that sunbathing in the summer for about 30 minutes can result in the production of over 10,000 IU of vitamin D and that once our skin makes about 20,000 IU, the ultraviolet light begins to degrade the vitamin so that we do not “overdose” on the sun. Vitamin D expert Dr. Vieth reports that there is no practical difference between vitamin D acquired from the sun and that acquired from food and supplements.

The Vitamin D Council reports that doses of 5,000 IU per day from all sources (sun, diet and supplements) are safe for most healthy people and that there are no reports of toxicity up to 10,000 IU per day. But the Council also warns that without calcium and magnesium in sufficient quantities, vitamin D supplementation will withdraw calcium from the bone and will allow the uptake of toxic minerals. As everyone metabolizes vitamin D differently, the best way to identify the optimal level of supplementation is to adjust the dosage to maintain target blood levels. The Vitamin D Council recommends that optimal health is supported by blood levels of 50-80 ng/mL (125-200nmol/L) as identified in a 25(OH)D vitamin D blood test.


High dose vitamin D treatment is broadly accepted in the medical community for people who are suffering from a severe deficiency but are otherwise in good health. There are two views on the best way to receive high dose vitamin D. The most common form of high dose vitamin D in the US is a prescription form of ergocalciferal also known as vitamin D2. But as vitamin D2 is less potent than vitamin D3, many doctors now recommend high dose vitamin D3 which can be purchased in a health food store or on-line.

VITAMIN D2 (50,000 IU/week)

Dr. Michael Holick of the Boston University School of Medicine recommends high dose vitamin D2 treatment for people whose 25(OH) blood levels are below 10 ng/mL (25 nmol/L). He proposes an oral dose of 50,000 IU/wk of vitamin D2 for 8 weeks followed by another blood test to check serum levels. If the levels are still inadequate, another 8-week course of 50,000 IU/week may be prescribed until blood levels reach 30 to 50 ng/mL (75-125 nmol/L). Once these target blood levels have been attained, patients prone to developing vitamin D deficiency may be encouraged to take 50,000 IU of D2 every 2 weeks to sustain their blood levels…or 1,000 IU a day of vitamin D3. He also suggests that exposure to direct sunlight for 5-10 minutes on the arms and legs between 10am-3pm during the spring, summer and fall can prevent further deficiency.

Ergocalciferol is available to U.S. doctors in prescription strength of 50,000 units in the brand names of Drisdol and Calciferol. As it is derived from plants rather than animals, ergocalciferol is considered Kosher.

VITAMIN D3 (4,000 IU/day)

Dr. Vieth (Mount Sinai Hospital in Toronto Canada) recommends that vitamin D3 is the preferred choice for supplementation. In 2001, a study involving 61 healthy men and women resulted in healthy increases in blood levels following daily intake of 4,000 IU of vitamin D 3-without an increase in blood calcium or urinary calcium excretion. After 2-5 months, the blood levels of participants increased to a range of 28-50ng/ml (69-125 nmol/L). Dr. Vieth has proposed a rule of thumb, that 4,000 IU of vitamin D3/day will increase 25(OH)D blood levels by 100nmol/L (40ng/ml) after 8 months of use and that any surplus vitamin D will remain in the body for approximately 2 months.

Dr. Vieth recommends a daily dose of 4,000 IU/day in order to maintain blood levels above 100nmol/L. He also clarifies that published cases of vitamin D causing elevated blood calcium (hypercalcaemia) have involved daily intake of 40,000 IU. Hypercalcaemia due to excessive vitamin D is generally accompanied by blood concentrations greater than 88ng/ml (220 nmol/L).

Dr. Vieth also suggests that high and infrequent dosing may result in blood level fluctuations without producing sustainable improvements in blood levels. Intake of lower doses of 2,000-4,000 IU daily rather than 100,000 IU once a month are more likely to produce the desired results.


Calcitriol is a steroid that is produced after vitamin D passes through the liver and kidneys. The Vitamin D Council warns against treating vitamin D deficiency with calcitriol (or its analogs) as it poses risks of hypercalcaemia (high blood calcium) and fails to replenish the body’s stores of vitamin D.


Non-compliance (failure to take medications) is common both with prescription drugs and vitamins. Pharmaceutical companies and researchers often seek to address this problem with a “one shot a year” approach to osteoporosis medication and occasionally with vitamins.

In 2010, professors at the University of Melbourne reported results of a study involving 2,256 women (aged 70 years or older and considered to be at high risk of fracture) who received an annual dose of 500,000IUs of D3 supplements for three to five years. They were surprised that the recipients of this high dose vitamin D regime had 26% more fractures and 15% more falls than the placebo group. Treatment of non-compliant people with mega doses of vitamin D does not seem to be the solution….as suggested by earlier research that lower doses ingested daily produce the best results.

There are a number of diseases for which vitamin D supplements can cause elevated blood calcium and possibly compromise the immune system. In these cases, supplements should only be taken under the supervision of a knowledgeable doctor.

For information on calcium and magnesium supplements that support high dose vitamin D treatment while also preventing osteoporosis, visit http://www.osteoporosis-vitamins.com/best-calcium-for-osteoporosis.html

We have many more Vitamins Help Articles Now Available.