How Much Vitamin D Do I Need to Take?

Dr. Sharon Orrange
Dr. Orrange is an Associate Professor of Clinical Medicine in the Division of Geriatric, Hospitalist and General Internal Medicine at the Keck School of Medicine of USC.
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We all remember stories about people getting rickets from lack of vitamin D in the “olden days.” While that is almost unheard of in most developed countries, we are seeing many people with subclinical vitamin D deficiency. Vitamin D deficiency is associated with osteoporosis, increased risk of falls, and possibly fractures. Vitamin D is also believed to be important to the immune and cardiovascular systems, and a factor in breast cancer risk. In 2006, 41% of Americans were vitamin D deficient.

How do you know if you are vitamin D deficient? A simple blood test with your primary care doctor to measure your 25-hydroxyvitamin D (25OHD) level will tell you. Insufficiency is defined as a vitamin D level less than 30 ng/mL (some argue 27, but 30 is the current line in the sand), and a vitamin D level less than 20 is deficient by all standards.

Why are we deficient in vitamin D? Changes in milk intake, use of sun protection, and obesity have accounted for the decrease in vitamin D in our adults.

Do we know that replacing vitamin D will help us? Yes—well, sort of. In many trials, vitamin D supplementation to achieve vitamin D (25OHD) levels of 28 – 40 lowered fracture risk.

Can my vitamin D level get too high? Though there doesn’t appear to be any toxicity associated with vitamin D supplementation, there are concerns when levels go above 50. It is rare that I see a patient’s level above 50 and I’ve been in private practice for 10 years. Ideally, you want to maintain your vitamin D level between 30 and 50 ng/mL.

So how much vitamin D do you need? This is highly debated but we appear to be settling on a consensus. First, think about getting it through your diet, which will happen only with vitamin D fortified dairy products. The Recommended Dietary Allowance (RDA) of vitamin D for adults through age 70 is 600 IU with the RDA increasing to 800 IU after age 71.

You will need more if you:

What supplements do I need to take to get my vitamin D level above 30? The two commonly available forms of vitamin D supplements are ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Studies suggest that vitamin D3 increases vitamin D levels faster than vitamin D2. For this reason I prescribe Vitamin D3 supplements.

Vitamin D3 is available in 400, 800, 1000, 2000, 5000, 10,000, and 50,000 unit capsules. 50,000 IU (1.25 mg) capsules are available as a prescription.

In patients with vitamin D levels less than 20, start with 50,000 international units (IU) of vitamin D3 once a week for six to eight weeks

After that, a maintenance dose of 800 – 2000 IU per day should be taken daily to maintain a vitamin D level above 30 ng/mL.

Three to four months after starting on vitamin D replacement, have your level rechecked to ensure you are on the right track.

Dr O.

The 50,000 IU (1.25mg) strength of vitamin D is prescription only, and may be covered by your insurance, but can be found for as low as $4 for a one-month supply (4 capsules). Lower strengths of vitamin D are available over the counter.

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