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Limited evidenceGeneral health

Multivitamin

The world's most popular supplement — with surprisingly little evidence of benefit for well-nourished people. Useful mainly as insurance for poor diets.

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What the science says

  • Preventing cardiovascular disease and extending life Limited evidence

    Large trials and systematic reviews consistently show no reduction in cardiovascular events or mortality from daily multivitamins in well-nourished adults.

  • Cancer prevention Limited evidence

    The Physicians' Health Study II (14,000+ men, 11 years) found a small (~8%) reduction in total cancer incidence — a modest effect not confirmed as practice-changing by later reviews.

  • Covering nutritional gaps Moderate evidence

    For people with restricted, monotonous, or low-calorie diets, a multivitamin plausibly and cheaply covers common micronutrient shortfalls — this is its most defensible use.

Dosage & safety

Studied doseOne daily dose of a standard formulation (~100% of daily values). Avoid megadose formulas — more is not better.
SafetyStandard formulations are safe. Watch total vitamin A (retinol) and iron — men and postmenopausal women usually should choose iron-free formulas.

How to take it

TimingTiming does not matter.
With food?With a meal — the fat-soluble vitamins absorb far better and it reduces the nausea a mineral-heavy tablet causes on an empty stomach.
Worth knowingCheck three numbers before buying: retinol (preformed vitamin A), iron, and B6 — those are the ingredients where a 'more is better' formula can actually harm you.

Interactions

With medications

  • levothyroxine

    The calcium and iron in most multivitamins block absorption of thyroid hormone. separate by at least 4 hours

  • tetracycline and fluoroquinolone antibiotics

    Calcium, magnesium, iron and zinc all chelate these antibiotics. separate by at least 2 hours before or 4-6 hours after

  • warfarin

    Vitamin K content varies between products and can shift your INR when you start, stop or switch brands. keep the same product and tell your anticoagulation clinic about any change

  • levodopa (without carbidopa)

    Vitamin B6 reduces levodopa's effectiveness when it is given unprotected. check the B6 content with your neurologist

With other supplements

  • individual vitamin A, iron or zinc supplements

    Doses stack silently — the ceiling that matters is your total across every product. add up the labels before taking anything on top of a multivitamin

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Is a daily multivitamin worth it?

For well-nourished adults, the evidence is limited: large trials show a multivitamin does not reduce heart disease or mortality. A multivitamin's most defensible use is as cheap insurance if your diet is restricted, monotonous or low in calories.

Do multivitamins prevent cancer?

The evidence is limited. The Physicians' Health Study II found a small (~8%) reduction in total cancer in men taking a multivitamin for 11 years, but later reviews did not treat it as practice-changing.

What should I check on a multivitamin label?

Pick a standard multivitamin at about 100% of daily values and avoid megadoses. Check the retinol, iron and B6 amounts, and men and postmenopausal women should usually choose an iron-free formula.

Should I take a multivitamin with food?

Yes. The fat-soluble vitamins in a multivitamin absorb far better with a meal, and food reduces the nausea mineral-heavy tablets cause on an empty stomach.

Scientific references

Where to buy

California Gold Nutrition, Multivitamin & Mineral, Two-A-Day, 60 Veggie Capsules

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