What level of vitamin D is considered normal?

Dear Alice,

I recently had lab work done that identified a vitamin D deficiency. My level was eight and my doctor says that 30 is considered a normal level. I was then prescribed a vitamin D2 pill to help bring my levels up. I just read something that said vitamin D3 is the preferred type to use as a supplement and that 30 isn’t considered the “normal” level anymore, that the number should be closer to 40 or 50.

A few questions: Is it better to use D3 or D2? What level is considered normal? What are the effects of vitamin D deficiency?

Dear Reader, 

Ahh, good old vitamin D is one of the most versatile and vital vitamins. It plays a major role in the body and a deficiency can lead to poor bone health or impaired calcium absorption. Vitamin D status is often measured by the level of serum concentration of 25-hydroxyvitamin D (or 25(OH)D) in the blood. Although D2 and D3 are used similarly by the body, they differ slightly in their chemical structure, and some studies suggest that D3 may lead to higher or sustained levels of 25(OH)D. The form D2 is often derived from plants, while D3 is found in animals or synthesized by sun exposure. Additionally, while both varieties are used as supplements for preventing vitamin D deficiency, the levels for a “healthy” status may differ depending on the person. 

Vitamin D, or calciferol, helps the body absorb calcium, which is necessary for strengthening bones, cell growth, and immune functions. Along with supplements and the sun, other food sources of vitamin D include fish and fish oils, egg yolk, infant formula, and foods that have added vitamin D, like milks and cereals. In addition to helping prevent weak bones, adequate vitamin D levels also help to prevent related conditions like rickets and osteoporosis. However, it’s important to note that excessive vitamin D intake could lead to adverse effects like high blood calcium levels. 

Since vitamin D levels are measured by serum concentrations of 25(OH)D in the body, they may be reported in nanomoles per liter or nanograms per milliliter depending on the source. The National Academies of Sciences, Engineering, and Medicine reports: 

  • Vitamin D deficiency is likely if the levels fall below 30 nanomoles per liter or less than twelve nanograms per milliliter. 
  • The range of vitamin D levels for a “healthy” individual is reported to be around 30 to 125 nanomoles per liter or 20 to 50 nanograms per milliliter. 
  • More than 125 nanomoles per liter or more than 50 nanograms per milliliter may lead to issues caused by overdosing of vitamin D. 

You mentioned a discrepancy between your doctor's number and your own research. It could be possible that your doctor was referring to the measurements of nanograms per milliliter, while you were referring to the nanomoles per liter or some other difference in the reporting. Regardless of the method of reporting, a vitamin D supplement like D2 or D3 is one way to make sure you are taking in enough vitamin D. For people aged 19 to 50 years old, the recommended daily amount is around 15 micrograms (mcg) or 600 international units (IU). 

Like most organic compounds, the levels of vitamin D in a person are influenced by dosage, age, gender, or intake regimen. For example, if vitamin D is synthesized by sun exposure, factors like the amount of sunlight or skin coverage can affect a person’s level. Some groups of people may also have a harder time creating vitamin D from the sun; this includes older people and people with darker skin. Additionally, individuals who don’t drink animal milk, infants who don’t drink formula, those who have a hard time absorbing fats, or those who don’t eat foods fortified with vitamin D are likely to have lower levels of serum concentration 25(OH)D. 

While there may be minimal differences between vitamin D2 and D3, consider speaking with a health care provider if you have questions about their suggested treatment or if you have been given a prescription. Ultimately, maintaining a “healthy” level of vitamin D is influenced by a variety of factors and working closely with a health care provider can help ensure you find the best supplements and treatment for your needs. 

Best of luck! 

Last updated Nov 17, 2023
Originally published Mar 06, 2014

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