This Is Exactly How Much Vitamin D3 You Should Be Taking Every Day

Nancy Rodriguez, PhD, RDN, FACSM, a professor of nutritional sciences at the University of Connecticut, says that back in her day, no one was talking about vitamin D supplements. “In the ‘60s and ‘70s, people weren’t slathering on sunscreen. We were basking in the sun with baby oil,” she says.

Though such intense sun worship had its own issues (like increasing the risk of skin cancer), it also meant that vitamin D deficiencies among the general population were rare. But these days, most of us work desk jobs and when we do go outside, we slather on sunscreen. While this is great for lowering the risk of skin cancer, it also means that we’ve become a nation of vitamin D-deficient people. According to a 2022 study published in Frontiers in Nutrition, 41% of people in the U.S. don’t get enough vitamin D.

Our bodies need vitamin D. The nutrient is responsible for more than 200 functions in the body, including bone strength, dopamine production (key for feeling happy), brain health, and immune support. While getting enough vitamin D is important, it’s also important not to take too much in supplement form, which is dangerous. That can make shopping for the perfect vitamin D supplement tricky. Curious about how much vitamin D3 you should take daily? Here’s everything you need to know.

What’s the difference between vitamin D2 and vitamin D3?

Like all nutrients, Allison Miner, EdD, RDN, a registered dietitian and assistant professor of nutrition and food studies at George Mason University, says the best way to get vitamin D isn’t in supplement form; it’s through food and, in this case, the sun. She says that foods with vitamin D include fatty fish, egg yolks, and fortified cereals, orange juice, and milk. Also, apparently, beef liver.

Sina Gallo, PhD, RD, a registered dietitian and nutritional sciences associate professor at the University of Georgia, explains that fatty fish, egg yolks, and beef liver all contain vitamin D3 while fortified foods contain both.

“Some research has suggested D3 can raise and maintain blood vitamin D levels more effectively and for longer than D2, although if taken daily they likely act similarly. Both forms need to be converted to the active form, calcitriol, to have any biological activity in the body,” Dr. Gallo explains. This is why vitamin D3 supplements are often recommended over vitamin D2; vitamin D3 raises vitamin D levels more efficiently and keeps levels elevated for longer.

When it comes to getting vitamin D from the sun, this is more complex. Dan Benardot, PhD, RD, FACSM, a registered dietitian and professor of practice at Emory University, explains that UV-beta rays from the sun create a compound called dehydrocholesterol. This compound is found in the skin and is then converted to vitamin D3.

“This way of getting vitamin D is not a safe nor sustainable source of vitamin D because of its potential for skin cancer,” Dr. Gallo says. She adds that how much vitamin D3 someone gets from the sun varies based on where they live, the time of day they’re getting sun exposure, and their melanin content.

Dr. Miner explains that the more melanin (the pigment that gives skin its color) someone has, the longer they have to be in the sun to experience the synthesis needed for producing and storing enough vitamin D. Someone who doesn’t have a lot of melanin (typically people with pale skin) needs less sun exposure.

How much vitamin D3 to take, if you’re going to take a supplement

All four nutrition experts say that signs you’re not getting enough vitamin D can be pretty vague, such as fatigue, brain fog, and feeling depressed. That means that you can be deficient in vitamin D and not even realize it. Dr. Rodriguez says that this is dangerous because it leads to absorbing less calcium from food, which can lead to weak bones. She says that it can also lead to muscle weakness.