Vitamin D: How Much to Take & How Much is Too Much

Q:  I keep reading about how vitamin D is so great, though I don’t really know how much to take since I see doses that range so much.  I want to be sure to take enough, but I’m worried about taking too much too.  Help!  

A:  I love vitamin D, and think everyone in America should be taking it during the winter months.  It’s made a huge difference in boosting my family’s immune systems.
It seems daily new research is coming out on the many different reasons to take vitamin D.

Vitamin D is best known for its use for bone and immune health, though studies listing more reasons to take it are growing all the time, with benefits for depression, cancer prevention and more.  Vitamin D is also inexpensive and is a tiny, easy to swallow pill (and it’s also available in liquids and chewables).

Here is a link on articles concerning vitamin D on our health blog.

Also, here are just a few recent studies on Vitamin D from the fantastic vitamin D council website:

Vitamin D and influenza

Vitamin D and pneumonia

Vitamin D and Breast Cancer

Vitamin D and depression

How much to take?
In the past, the RDA of vitamin D was only 400IUs, which was recently raised to 600IUs.  The research of the past several years has found again and again that significantly higher dosages are needed for optimal health.

Dr. Weil, the famous holistic health physician personally recommends 2,000IUs a day of vitamin D.

WebMD has even reported on a study that recommended a daily dosage of 2,000IUs a day for children.

The Vitamin D Council recommends 5,000IUs daily of vitamin D for adults.
I personally take around 5,000IUs of vitamin D a day, and my four year old daughter takes roughly 10,000IUs a week in divided doses.  Since we are outdoors all the time in the summer, we only supplement with vitamin D in the colder months.

Vitamin D, how much is too much?
Vitamin D is a fat soluble vitamin, which means it is stored in the body, so unlike vitamin C it can be toxic in excessive dosages.  Still, that is rare, particularly since vitamin D deficiency is so common.

One four year study of 423,000 people found that only 3% of the people had exceeded safe levels of vitamin D in the body, whereas 62% of the study’s population was at risk “of heart attack and death” because of low serum vitamin D levels.

The vitamin D council (a great resource on vitamin D) says that excessive levels may develop if a person took, “more than 10,000 IU/day (but not equal to) everyday for 3 months or more. However, vitamin D toxicity is more likely to develop if you take 40,000 IU/day everyday for 3 months or more.”

For children they recommend the following limits for vitamin D:

  • For children that weigh 25 lbs or less, more than 50,000 IU in 24 hours or 2,000 IU/day for over three months is too much and potentially toxic.
  • For children that weigh between 25 and 50 lbs, more than 100,000 IU in 24 hours or 4,000 IU/day for over three months is too much and potentially toxic.
  • For children that weigh between 50 and 75 lbs, more than 150,000 IU in 24 hours or 6,000 IU/day for over three months is too much and potentially toxic.
  • For children that weigh between 75 lbs and 100 lbs, more than 200,000 IU in 24 hours or 8,000 IU/day for over three months is too much and potentially toxic.

It’s always a good idea to get a blood draw with your yearly checkup from your doctor.  When I had a blood test last year my doctor said I was one of the few people she saw that actually had good vitamin D levels.

The US Department of Health and Family Services reports that almost no one has vitamin D levels that are too high and that in general, younger people have higher levels than older people, and men generally have higher levels than women.  

By race, non-Hispanic blacks have the lowest levels of vitamin D, with non-Hispanic whites having the highest.  They also report that the majority of Americans have lower than the minimum recommended levels of vitamin D.

Certain other groups have an increased likelihood of being vitamin D deficient.

  • Breastfed infants, since human milk is a poor source of the nutrient. Breastfed infants should be given a supplement of 400 IU of vitamin D each day.
  • Older adults, since their skin doesn't make vitamin D when exposed to sunlight as efficiently as when they were young, and their kidneys are less able to convert vitamin D to its active form.
  • People with dark skin, because their skin has less ability to produce vitamin D from the sun.
  • People with disorders such as Crohn's disease or celiac disease who don't handle fat properly, because vitamin D needs fat to be absorbed.
  • Obese people, because their body fat binds to some vitamin D and prevents it from getting into the blood.

Which form to take?
Vitamin D is available in two forms, D2 and D3.  Vitamin D3 is the superior form since it is the most biologically active in the body.  D3 is most often sourced in supplements from lanolin, but can also be from fish liver oil.  There are also new vegan vitamin D3 supplements for people avoiding animal products.