What it is
Regulatory status: dietary supplement; no standard US definition fixes the included nutrients or doses
Mechanism evidence: human
At a glance
What it is, why people use it, the evidence, and what to know before trying it.
Why people use it
- Fill micronutrient intake gaps
- General health maintenance
- Cognitive support in older adults
Evidence at a glance
Multivitamins can fill dietary gaps, but benefits cannot be inferred without the product label and baseline diet. Large prevention trials do not show a universal reduction in cardiovascular disease or cancer; some recent older-adult trials report modest cognitive outcomes.
Confidence: moderate
Safety & interactions
Known side effects, interactions and use limits from reviewed sources.
Risk depends on the formula. Vitamin A, iron, vitamin B6, niacin, folic acid and other ingredients can be harmful at excessive doses or in susceptible people, and products can duplicate nutrients from other supplements.
- Iron-containing products in people advised to avoid iron
- High-dose vitamin A in pregnancy
- Nausea
- Constipation or diarrhea
- Excess intake of individual nutrients
- Vitamin K with warfarin
- Iron or calcium with some medicines
- Overlapping fortified foods and supplements
Forms and variants
This review does not automatically apply to:
- prenatal vitamins
- single-nutrient supplements