Exactly How Long To Wait To Retest Vitamin D Levels After Starting A Supplement

So, say your health care provider confirmed with a 25(OH)D test that you need to get more of the sunshine vitamin into your system, stat—and that you promptly started (and have diligently stuck to) a daily vitamin D supplement routine. You might feel antsy to retest your vitamin D status and confirm that your habit change is paying off—but not so fast!

While we all want immediate gratification, you’ll have to be a little patient here. The reason: “Vitamin D is fat-soluble, so vitamin D supplementation goes toward replenishing the vitamin D stored in fat, in addition to serum levels,”* Henderson explains. “As these storage levels are replenished, serum levels then start to rise.”*

As a result, “waiting three months to retest your 25(OH)D status can help give you a more accurate reading of how well your supplement has done in replenishing your whole-body vitamin D levels,”* she adds. Research agrees, with studies similarly suggesting health care practitioners wait 12 weeks before rechecking a patient’s vitamin D status after starting them on a supplement or adjusting the potency of that supplement. 

There’s nothing you can do to speed up this process, but you can increase your chances of success by ensuring you take in some fat alongside your vitamin D supplement in order to promote optimal absorption.* (Remember, it’s fat-soluble!) Better yet, opt for a supplement that contains vitamin D3 and a source of fat so you don’t have to wait for snack- or mealtime to get your daily dose of the sunshine vitamin. (mbg formulated our vitamin D3 potency+ with a unique trio of organic, virgin oils so you can take your daily dose of D whenever is most convenient for you.)*