“For people with known low vitamin D levels, I typically recommend choosing a vitamin D3 supplement of 5,000 IU and taking it daily for eight to 12 weeks before retesting blood levels,” suggests Crouch. “That said, seasons of the year, typical sun exposure, skin tone, and body fat should all be considered, as these traits could increase a person’s supplement needs.”*

Of course, there is a place for some of the lower-dose vitamin D supplements you see out there (think anything less than 3,000 IU)—specifically when someone is taking multiple supplements that contain vitamin D3, like a multivitamin and a bone or immune health supplement, highlights dietitian Jess Cording, M.S., R.D., CDN.* A lower-dose product can also be an easy way to augment your current D routine in the winter months, she suggests.

In these cases of multiple D inputs, Ferira explains that you’ll want to “think of your daily D3 supplement as your critical foundation to achieve and maintain healthy vitamin D levels, and approach the lesser but useful bits of vitamin D from a multivitamin, immune complex, diet, and sunshine as a complementary, extra, bonus if you will.”*

Generally, though, you probably need to take more vitamin D than you think, especially if you have insufficient or deficient levels since even those with already-healthy levels need 3,000 IU per day just to avoid dipping into a state of insufficiency. Consider a high-potency option, such as mbg’s vitamin D3 potency+ (which offers 5,000 IU of sustainable organic algal vitamin D3) or another one of our favorite vitamin D supplements.* (And for more product recommendations, check out our vitamin D supplement roundup.)