To help you achieve vitamin D sufficiency for life (which all good science shows requires supplementation),* let’s clear up just where you want your vitamin D levels to be—and stay. 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.”* She goes on to say, “Some people track their blood pressure as an indication of cardiovascular health. I’m one of those people, but I also track my 25(OH)D level at least annually to inform my vitamin D health state. It’s that important.” Ferira puts it this way: “I personally don’t like to confuse folks by even mentioning 30 ng/ml in the same breath as ‘vitamin D sufficiency.’ I prefer to think of 30 as the risk or warning zone. It’s the cutoff for inadequacy, so you don’t strive for it, you avoid it with intention.” Unfortunately, a large chunk (41%) of the U.S. adult population is in the “warning zone” (< 30 ng/ml)2, and they probably don’t even know it. This means they are vitamin D insufficient. Another term used is hypovitaminosis D. To make it simple, not enough vitamin D. “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.” Ferira adds this analogy, “Aiming for 30 ng/ml is like signing up and paying for four years of college but never attending any classes, taking any tests, or graduating. It’s a bad investment, aims too low, and is going to hurt eventually.” 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.” Considering a 3-ounce serving of trout4 (which is the best whole-food source of vitamin D out there) only offers 645 IU and that a number of factors (such as your skin tone and where you live) prevent most people from getting significant amounts of vitamin D from the sun, you’re left with one stellar option: a high-quality, high-potency vitamin D supplement.* 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. Not many supplements check all of these boxes, which is why mbg formulated vitamin D3 potency+ to provide 5,000 IU of vitamin D3 (from a sustainable, plant-origin source: algae!), plus a trio of healthy organic fats from extra-virgin olive, flaxseed, and avocado oils.* 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. In terms of follow-up testing, Henderson recommends retesting your vitamin D status every eight to 12 weeks and working with your health care practitioner to make any tweaks needed.