Q&A: Can you overdose on vitamin D?

My doctor has recommended a large daily dose of vitamin D to counteract osteopenia (thinning bones). Is it possible to overdose on the vitamin? —J.S., Orinda, Calif.

Yes, but it takes huge doses: at least 10,000 international units (IU) a day for several years. Such amounts can damage the kidneys, bones, and nervous and cardiovascular systems. But reaching them would require a lot of pills or even injections. Most people should consume between 600 and 1,000 IU a day from food or supplements, depending on their age and level of sun exposure. Multivitamins usually supply about 400 IU, enough for most people to reach those levels. But you may need a larger supplement if you are older than 50 or so, heavier, have darker skin, or rarely get out in the sun. If the dose your doctor suggests is higher than the 1,000 IU a day typically recommended to strengthen bones and provide other benefits, ask why you need so much.

This article first appeared in the July 2008 issue of Consumer Reports on Health.

Read more on the surprising benefits of vitamin D (free) and on how vitamin D can help in the prevention of osteoporosis (subscribers only).

Comments

[Robert McMullen, MD]

The minimum dose for an adult is 4000 I.U. per day. Taking 50,000 IU once a week is a good strategy. 50% of doctors are now aware that we have completely overlooked the hormone calciferol that is mistakenly called a vitamin. A vitamin is a brick to build a house. Vitamin D is the house-- a large molecule that our body produces and needs. And most cells have a receptor on the nucleus for vitamin D.
Robert McMullen, MD

[Daryl]

Vitamin D is great to take on a regular basis
because of all the great things that it does
provide when taking it on a constant basis.

[Daryl Saari]

I found this information very useful, and will tell my family
about this, because they are always looking for better solutions and ideas. Thank You very much, and let me know about any other ideas you can offer, by leaving a comment back to me about anything else that i may have missed that you recommend. Thanks!

[Jean Bettanny]

Yes, it's very easy to overdose on Vitamin D. I was taking 3000 i.u. per day (on doctor's rec.) and developed an alarming case of polydipsia (excessive thirst). (Thought I suddenly had diabetes!)

Lowering the dosage stopped it. I cannot take more than 1600 i.u., or else the symptom returns. It's definitely a repeatable experiment.

I'm surprised this is not generally known!

I need to take as much Vitamin D as possible since I assiduously avoid the sun and have osteopenia.

[Kate]

Wennye',

1.25 mg of D3 is 50,000 I.U.

[Wennye' Edwards]

I have been prescribed 1.25MG of vitamen D by my physician, how many IU's is this equivalent. I take it once a week.
Thanks, Wennye'

[Paul R]

Wow. Thanks for the heads up, Greg. I'm going to have to cut down on my polar bear liver consumption too...:)

[Greg Krohne]

This reminds me of some bit of trivia about eating liver. Supposedly, polar bear liver is so high in Vitamin D (and/or Vitamin A?) that it is considered poisonous. Since then, I have carefully avoided consuming polar bear liver.