Truly Optimal Vitamin D Levels Are Higher Than You Might Think

Vitamin D is a hot topic these days, and given the many (really, many!) roles it plays in the body, it's well-deserving of the attention. The thing is, though, there's still a bit of confusion out there about how much vitamin D we really need—and what levels we should maintain in our body for truly optimal health for life.

Vitamin D is a fat-soluble vitamin, preprohormone, and full-on hormone (i.e., in its active form in the body) that's essential for whole-body health.* Vitamin D3 is synthesized in our skin from UVB sunlight exposure, which is how it earned its nickname "the sunshine vitamin."

We can also get some vitamin D from specific foods (though, not nearly enough to support sufficient vitamin D status).

Let's begin with a quick breakdown of how doctors and researchers measure vitamin D levels (aka, your vitamin D status) in the body. When you ask your doc to test your vitamin D, they perform a blood test to measure your serum total 25-hydroxyvitamin D, or 25(OH)D, for short, explains mbg's director of scientific affairs Ashley Jordan Ferira, Ph.D., RDN.

Quantified in nanograms per milliliter (ng/ml) units, Ferira explains that, "your 25(OH)D level is a biomarker that reflects your whole-body vitamin D status from circulating blood levels. Vitamin D is the starting vitamin input, and that essential micronutrient is hydroxylated in your liver to 25(OH)D to travel around the body, available to your various organs for a variety of critical health functions."*

If you've ever had your serum vitamin D levels tested or done a quick search online about healthy levels, you've probably come across the idea that 30 ng/ml is the goal—but that's not really the case. In truth, 30 ng/ml is just the bottom cutoff for vitamin D "sufficiency."1

"This is the bare minimum level to avoid major issues known to occur with vitamin D deficiency, including bone issues and poor thyroid health," explains board-certified endocrinologist Brittany Henderson, M.D., who specializes in hormones (including vitamin D) in her clinical practice. That said, "higher levels of serum 25(OH)D have consistently been associated with improvements in mood, enhancement of the immune system, and more." 

So if 30 ng/ml really doesn't cut it for optimally supporting your health and well-being, what vitamin D levels should you strive to achieve and maintain?

"As an endocrinologist, I know that achieving optimal serum 25(OH)D levels in the 50+ ng/ml range is imperative for immune health, bone health, and more," Henderson says. "This is the average or median level at which most association studies show various benefits, including immune health, balanced mood, and more."

And the tool to achieve that level of 50 ng/ml is clearly vitamin D3 supplementation, according to Henderson's clinical expertise with hundreds of patients (plus, the collective D science to date).*

While hitting 30 ng/ml is a start (especially if you're starting out with levels below 20 ng/ml, which means you're clinically deficient1), it's not the goal.

"We are consistently undertreating patients when we stop at 30 ng/ml," Henderson continues. "Our population is heavily vitamin D deficient and targeting an optimal level of 50 ng/ml has an enormous impact on all aspects of human health."

If you think relying on food and sun alone will help you reach that 50 ng/ml mark (and stay there), newsflash for you: It's just not possible (with food) and unwise (with sun).

Ready for a little math? Ferira breaks it down for us: "Pharmacokinetic research3 shows that it takes 100 IU of vitamin D to increase a normal-weight adult's serum D levels by about 10 ng/ml. So, that means that in order to achieve 50 ng/ml, you need 5,000 IU of vitamin D per day."

That means vitamin D3, which is the body's preferred form.* "The formulation of vitamin D3 is the most important variable," says Henderson. "It has to be packaged as highly bioavailable or it just won't work!"

Specifically, "since vitamin D is a fat-soluble vitamin, it is important that it be packaged with fats for maximal absorption,"* she adds. And, remember, you'll need 5,000 IU per day to hit that 50 ng/ml mark.

So, how often should your doc test your vitamin D status? You might be surprised by the answer. It turns out that you can start a vitamin D3 supplement routine before or after you test your 25(OH)D level. Ferira explains: "Getting a baseline 25(OH)D test result is informative but in no way imperative. In reality, the daily D3 supplementation practice is way more important than an overzealous tracking of your serum status."

If you're able to get a baseline 25(OH)D test, great. It will help you track the progress of the supplement so your health care provider can help pivot and individualize your dosing as needed. "For example, folks with more body fat will require proportionately more vitamin D1, about two to three times more, per the science,"* says Ferira.