Your body needs vitamin D to function properly, but your vitamin D level may start to decline as you age. To get enough vitamin D, you need healthy skin, a healthy liver, healthy kidneys, and the ability to get enough sunlight, all of which could change as you get older.
Why Your Vitamin D Levels Might Decrease as You Age
Vitamin D is a hormone that requires sunlight, skin, the liver, and the kidneys to fully operate, said Matthew Badgett, MD, a lifestyle medicine and internal medicine specialist at the Cleveland Clinic.
“Older people tend to get less sunlight, and their skin has fewer vitamin D precursors,” Badgett said.
Aging may also affect how the body processes vitamin D. The liver may produce less of an enzyme called 25-hydroxylase, which helps activate vitamin D3, although Badgett said this reduction has only been shown in mice, not humans.
Badgett added that vitamin D production may also decrease as kidney function declines with age, especially in older adults with chronic kidney disease.
How to Boost Vitamin D Levels If You’re Deficient
If your doctor finds that your vitamin D level is low, there are many steps you can take to increase it. You can start by spending more time outside.
“Of all the issues, reduced skin production is likely the major limiting factor. This means older people may need more sunlight to produce adequate amounts,” Badgett said. However, he added that it’s important to avoid getting sunburn, as this can increase the risk of skin cancer.
Several common medications can also cause sun sensitivity, such as blood pressure medications and certain antibiotics. So, it’s best to avoid staying out in the sun for more than 15 minutes.
If you live in a cold, dark climate, supplementation may help. “This will improve vitamin D levels as well, but may not fully capture the benefits of sunlight,” Badgett said. “Higher doses are often needed with age.”
On that note, make sure you speak with a doctor or pharmacist about how much vitamin D you need. At higher doses, vitamin D toxicity can occur.
You can also increase your vitamin D intake from diet, but it is difficult to get enough through diet alone. Your best bet may be upping your vitamin D intake through a combination of sunlight and diet and, if that doesn’t work, adding a supplement.
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Ellison DL, Moran HR. Vitamin d: vitamin or hormone? Nursing Clinics of North America. 2021;56(1):47-57.
Asif A, Farooq N. Vitamin d toxicity. In: StatPearls. StatPearls Publishing; 2025.
O’Neill is a reporter who covers new medical research and addiction. She previously worked at SELF magazine and Health.com, and she was a 2020 fellow at the Association of Health Care Journalists.
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