The best way to get vitamin D depends on where you live, your skin tone, and your diet, but for most people it comes down to a combination of brief sun exposure, vitamin D-rich foods, and supplements when needed. No single source is enough for everyone year-round, so understanding how each one works helps you fill the gaps.
Sunlight: The Most Efficient Source
Your skin manufactures vitamin D when ultraviolet B (UVB) rays hit it directly. This is the fastest way to raise your levels, and for many people during warmer months, it’s all that’s needed. The general guideline from Germany’s Federal Office for Radiation Protection: expose your face, hands, and arms to sunlight for about half the time it would take your unprotected skin to burn, two to three times per week. For someone with fair to medium skin at a UV index of 7 (a typical summer midday), that works out to roughly 12 minutes.
People with darker skin need more time because higher melanin levels slow UVB absorption. If you burn in 40 minutes rather than 25, your target exposure is longer. The key is staying well short of a sunburn, which means you’re not trying to tan. You’re just giving your skin a brief window of unprotected exposure before covering up or applying sunscreen.
Geography matters enormously. If you live north of the 37th parallel (roughly the latitude of Los Angeles), your skin produces little to no vitamin D from November through March. The sun sits too low in the sky for enough UVB to reach you. That covers most of the United States, all of Canada, the UK, and northern Europe. During those months, you need to rely on food and supplements instead.
Food Sources Worth Prioritizing
Very few foods naturally contain meaningful amounts of vitamin D, which is why deficiency is so common. The richest natural sources are fatty fish: salmon, mackerel, sardines, and trout. A single serving of cooked salmon can deliver 500 to 700 IU, which is close to an entire day’s recommended intake for most adults (600 to 800 IU depending on age). Canned tuna and sardines provide smaller but still useful amounts.
Egg yolks contain vitamin D, though at much lower levels, around 40 IU per yolk. Cod liver oil is one of the most concentrated sources available, often exceeding 1,000 IU per tablespoon, but the strong flavor limits its appeal. Beef liver and certain mushrooms exposed to UV light also contribute small amounts.
Fortified foods fill in the rest for many people. Milk, orange juice, breakfast cereals, and plant-based milks are commonly fortified with 100 to 150 IU per serving in the United States. If you drink two glasses of fortified milk and eat one serving of fatty fish in a day, you’re likely meeting your target through food alone. Most people don’t eat this way consistently, though, which is where supplements come in.
When Supplements Make Sense
If you live at a northern latitude, spend most of your time indoors, have darker skin, or simply don’t eat much fish, a daily vitamin D supplement is the most reliable way to maintain adequate levels. Vitamin D3 (the form your skin produces naturally) is generally preferred over D2, as it raises blood levels more effectively and sustains them longer.
Most adults do well with 1,000 to 2,000 IU daily, though people with confirmed deficiency may need higher doses for a limited period under medical guidance. The tolerable upper limit for adults is 4,000 IU per day. Going significantly above that over time can lead to toxicity, which causes calcium to build up in your blood, potentially leading to nausea, kidney problems, and weakness. This only happens from supplements or very high-dose fortified foods. You cannot overdose on vitamin D from sunlight because your skin self-regulates production.
How to Absorb More of What You Take
Vitamin D is fat-soluble, meaning it dissolves in fat rather than water. Taking your supplement with a meal that contains some fat improves absorption. This doesn’t require a high-fat meal. A handful of nuts, avocado on toast, or eggs will do. Some vitamin D absorbs even without dietary fat, but pairing it with food is a simple way to get more out of each dose.
Magnesium plays a surprisingly important role that most people overlook. Every enzyme involved in converting vitamin D into its active, usable form requires magnesium as a cofactor. This includes the processing steps that happen in both your liver and kidneys. If your magnesium intake is low (and surveys suggest most Americans fall short), your body may struggle to activate the vitamin D you’re getting from any source. Good magnesium sources include dark leafy greens, nuts, seeds, beans, and whole grains.
Putting It All Together
The practical approach for most people looks like this: get brief, regular sun exposure during the months when UVB is available in your area. Eat fatty fish once or twice a week and include fortified foods when convenient. During the winter months, or if your lifestyle limits sun exposure, take a D3 supplement of 1,000 to 2,000 IU with a meal containing some fat. Make sure your diet includes enough magnesium to support vitamin D activation.
If you suspect you’re deficient, a simple blood test measuring your level of 25-hydroxyvitamin D gives a clear answer. Most experts consider 20 to 50 ng/mL an adequate range, with levels below 20 ng/mL indicating deficiency. Testing is especially worthwhile if you have risk factors like limited sun exposure, obesity, digestive conditions that impair fat absorption, or darker skin tone.