Experts Say Over 60% Of The World Lacks This 1 Vitamin, And It Increases Your Risk Of Illness

It’s common for PCPs to recommend between 1,000 to 2,000 IUs per day of vitamin D3, Stadler said. Holick thinks adults should be on a higher amount than this, though.

“Typically, I recommend adults should be on minimum 2,000 units per day — and most I recommend 5,000 units a day because you want to get your blood level, in my opinion, of [vitamin D] between 40 and 60 ng/mL, [but] up to 100 is perfectly safe,” said Holick.

Once you get the go-ahead from your doctor, you can buy vitamin D supplements online or in stores like CVS and Walgreens. You’ll likely find vitamin D3 and vitamin D2 on the shelves, but vitamin D3 is more readily available and tends to be more recommended. Holick said vitamin D2 is perfectly acceptable, too, and is often preferred by vegans.

While it’s better to get some nutrients directly from food, that isn’t easy or potentially even possible with vitamin D. Oily fish, milk and orange juice are all good for increasing vitamin D levels, but can’t do so to the level necessary, said Holick. The same goes for the sun, which also carries a risk of skin cancer with too much exposure. 

Holick said he recommends vitamin D supplementation to all of his patients, friends and family.

“You cannot get enough from your diet. You aren’t able to get enough from sunlight, unless you’re a … hunter-gatherer, so vitamin D supplementation is essential,” Holick said.

Older adults and people with darker skin are at higher risk of vitamin D deficiency, Stadler added. But, once again, it’s advisable for most people to take a supplement.