Vitamin absorption: How to get the most from supplements and food

Fact: eating a vitamin doesn't mean your body uses it. What you eat with a vitamin, when you take it, and what medicines you’re on change how much your body actually absorbs. This guide gives specific, actionable tips so you waste less money and feel better faster.

Start with food first. Real food delivers cofactors—minerals, healthy fats and enzymes—that help vitamins be absorbed. For example, fat-soluble vitamins (A, D, E and K) need fat. Eat a handful of nuts, a spoon of olive oil, or some avocado with a salad to boost uptake. Water-soluble vitamins (C and the B group) don’t need fat, but they absorb best from fresh food or a light meal rather than a heavy, greasy plate.

Quick rules that work

1) Take vitamin D and omega-3 with a meal that contains fat. 2) Spread B vitamins through the day—one dose in the morning and, if needed, another at lunch—so your body uses them steadily. 3) Separate calcium and iron by at least two hours. Calcium blocks iron absorption when taken together. 4) For iron, take it with vitamin C or orange juice to increase absorption, and avoid coffee, tea or dairy within an hour. 5) Choose the right form: methylfolate and methylcobalamin are better for people with certain genetic differences than folic acid and cyanocobalamin.

Timing matters. Take minerals like magnesium at night if they relax you. Take B12 in the morning because it can be stimulating. If a supplement causes stomach upset, try it with food or switch to a different form—iron glycinate is gentler than ferrous sulfate for many people.

Drug and condition interactions to watch

Certain medications lower vitamin levels. Long-term use of proton pump inhibitors and H2 blockers can reduce B12 absorption. Metformin is commonly linked to lower B12. Anti-seizure drugs such as phenytoin can affect vitamin D and folate levels. If you’re on these meds, ask your doctor for periodic blood tests and consider supplements tailored to your needs.

Kidney or liver disease, age, and surgeries that remove parts of the gut also change how you absorb nutrients. Older adults absorb B12 less efficiently and may need sublingual or injected forms. People who had gastric bypass often need lifelong B12, iron and vitamin D monitoring.

Finally, quality matters. Pick supplements that list active forms and third-party testing. If you take multiple pills, simplify: a well-balanced multivitamin plus targeted supplements for deficiencies often beats high doses of everything. Test before you guess—blood tests tell you what you really need and prevent unnecessary or harmful excess.

Quick checklist: get a basic blood panel (B12, iron, ferritin, vitamin D) yearly if you take long-term supplements or meds; note any symptoms like fatigue, numbness, brittle nails. Avoid taking very high doses of vitamin A (retinol) unless supervised—too much can cause harm, especially in pregnancy. Talk to your pharmacist about timing with prescription meds. Small changes in timing or pairing often makes a big difference.