This article is for general informational purposes and is not a substitute for professional medical advice. Always talk to a qualified health provider about your specific situation.
Vitamin D is unusual among nutrients because your body can make it from sun exposure on skin, which means diet is only part of the picture — and deficiency is common even in sunny regions, mostly because of limited sun exposure and diet alone rarely providing enough.
Common signs, though often subtle
Mild to moderate deficiency often causes no obvious symptoms, which is part of why it’s frequently caught on routine bloodwork rather than from how someone feels. When symptoms do appear, they can include fatigue, bone or muscle aches, and in more severe or prolonged deficiency, increased fracture risk. These symptoms overlap with many other conditions, so a blood test is the only reliable way to confirm a deficiency rather than guessing from symptoms alone.
Why deficiency is so common
Sunscreen, indoor lifestyles, higher latitudes, darker skin (which produces vitamin D less efficiently from the same UV exposure), and winter months all reduce the amount your body makes on its own. Diet alone typically can’t fully close that gap, since very few foods naturally contain much vitamin D.
Food sources worth knowing
- Fatty fish (salmon, mackerel, sardines) — among the richest natural dietary sources
- Egg yolks — a modest but meaningful contributor
- Fortified foods — many countries fortify milk, some plant milks, and certain cereals with added vitamin D specifically because natural dietary sources are so limited
- Mushrooms exposed to UV light — naturally low in vitamin D, but UV-treated mushrooms (often labeled as such) contain meaningfully more
When to consider a supplement
If bloodwork confirms a deficiency, or if you have limited sun exposure and rarely eat the foods above, a supplement is often the most reliable way to correct levels — diet and sun exposure alone are frequently not enough once a deficiency is established. Because appropriate dosing depends on how deficient someone is and their individual health picture, this is worth discussing with a doctor rather than self-prescribing a high dose, since vitamin D is fat-soluble and can accumulate to harmful levels if taken in excess over time.