Multivitamin Dosage: How Many to Take and When
Take one multivitamin a day: the serving on the label, and don’t double up. Look for about 100% of the Daily Value of each nutrient, and nothing over NIH’s upper limits.
By Erin Rose Updated October 8, 2026 How we score
This pick has iron. FDA requires this warning on iron products: “WARNING: Accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under 6. Keep this product out of reach of children. In case of accidental overdose, call a doctor or poison control center immediately.”
No iron: NATURELO One Daily Multivitamin for Men, $0.40 a day at list price. Which do you need? See every multivitamin we score.
How many, by situation
| Your situation | How many | Notes |
|---|---|---|
| Most adults who take one | One day’s serving | 1 tablet for most brands. For Ritual Women 18+ and Thorne 2/Day, it is 2 capsules. |
| Healthy, with a varied diet | None needed | Most healthy adults who eat a varied diet don’t need one. See who does. |
| After bypass or sleeve surgery | As your surgery team directs | Your surgery team sets the dose. |
| Drug-tested athlete | One day’s serving | Thorne Basic Nutrients 2/Day is on NSF Certified for Sport, $1.33 a day at list price. Because of its niacin, skip a separate B-complex. |
If you could become pregnant: the US Preventive Services Task Force advises 400 to 800 mcg of folic acid a day (USPSTF 2023). A regular multivitamin is not a prenatal. Iron needs rise to 27 mg a day in pregnancy (NIH). The trials behind the folic acid advice used folic acid; NATURELO and Ritual use methylfolate instead. Ask your doctor which to take.
How much of each nutrient
Look for about 100% of the Daily Value (the “% DV” column on the label). In the large trials, side effects were mostly minor stomach upset (NIH). Risk comes from too much of one nutrient. The number to watch is NIH’s upper limit: the most you should get in a day. The table shows the six nutrients most likely to pass it. One multivitamin we score passes a limit on its own: Thorne Basic Nutrients 2/Day has 80 mg of niacin in one day’s serving, against NIH’s 35 mg limit (229%). Its niacin is niacinamide, which rarely causes flushing, but NIH’s limit still counts it.
Share of NIH’s adult upper limit in one day’s serving, from each label. “–” means the label lists none. Bold: half the limit or more. The niacin limit counts only niacin from supplements and fortified foods; the others count everything you eat.
| Nutrientupper limit | Nature Made with Iron | NATURELO for Women | NATURELO for Men | Ritual Women 18+ | Thorne 2/Day |
|---|---|---|---|---|---|
| Vitamin D100 mcg | 25% | 20% | 22% | 50% | 50% |
| Iron45 mg | 40% | 20% | – | 18% | – |
| Zinc40 mg | 38% | 25% | 25% | – | 38% |
| Niacin35 mg | 57% | 46% | 50% | – | 229% |
| Vitamin B6100 mg | 2% | 2% | 2% | – | 20% |
| Selenium400 mcg | 18% | 13% | 13% | – | 50% |
The products in the table, each on a public testing list: Nature Made Multi Complete with Iron, NATURELO One Daily Multivitamin for Women, NATURELO One Daily Multivitamin for Men, Ritual Essential for Women 18+ Multivitamin, Thorne Basic Nutrients 2/Day.
Two limits the table leaves out. Vitamin A: NIH’s upper limit of 3,000 mcg (10,000 IU) a day of preformed vitamin A (retinol) applies to all adults, not only in pregnancy. It counts food and pills, and it was set to avoid liver problems and birth defects. Beta-carotene doesn’t count toward it. Folic acid: NIH’s limit is 1,000 mcg a day of folic acid from pills and fortified foods; folate in food doesn’t count. The reason: large amounts can fix the anemia of a low B12 while the nerve damage goes on, which can hide the shortage. Vitamin K: if you take warfarin or another blood thinner, ask your doctor before any multivitamin with vitamin K. One more: Thorne Basic Nutrients 2/Day has 20 mg of B6. That is under the US limit of 100 mg but over the 12 mg limit Europe’s food safety agency set in 2023 (NIH).
Can you take 2 multivitamins a day?
Not unless the label’s serving is 2, or a doctor tells you to. A second serving doubles everything, including the nutrients in bold above. In the big trials, people took one Centrum Silver a day.
The real risk: stacking
Trouble starts when you add other pills and fortified foods. In a study of 90,771 adults, 10% to 15% of multivitamin users took in too much vitamin A, iron and zinc, and about half took in too much niacin (NIH). If you also take a separate vitamin D, zinc, B-complex or iron, add them up against the table above.
When to take it
Any time of day you’ll remember. The trials had people take it daily and did not test timing. Taking it with a meal helps: vitamins A, D, E and K are fat-soluble, so some fat in the meal helps them absorb (NIH), and food can ease an upset stomach. If it has iron, take it apart from coffee, tea and calcium pills.
When you don’t need one
- You are healthy and eat a varied diet. Most people like you don’t need one. The US Preventive Services Task Force found “not enough evidence” to say whether a multivitamin prevents heart disease or cancer, which is not a recommendation against it (USPSTF 2022). See who does need one.
- You already take a multivitamin or a prenatal. Don’t add a second one.
Questions
How many multivitamins should I take a day?
One day’s serving, as the label says. That is 1 tablet for most brands; for Ritual Women 18+ and Thorne 2/Day it is 2 capsules. Don’t take a second serving or a second multivitamin unless a doctor tells you to: it doubles everything, including iron, vitamin A and zinc.
When should I take a multivitamin?
Any time of day you’ll remember. Taking it with a meal helps: vitamins A, D, E and K need some fat to absorb, and food can ease an upset stomach. If it has iron, take it apart from coffee, tea and calcium pills, which can lower iron absorption (NIH).
Do I actually need a multivitamin?
Most healthy adults who eat a varied diet don’t. The USPSTF found “not enough evidence” to say whether one prevents heart disease or cancer (USPSTF 2022). Some people may want one, such as many people over 50 and vegans. Who needs one.
Can you take too many multivitamins?
Yes. The usual way is stacking: two multivitamins, or one plus separate pills with the same nutrients. Vitamin A, iron, zinc and niacin are the ones to watch. Add them up against NIH’s upper limits.
Is a one-a-day or two-a-day better?
Neither is proven better for health. A two-a-day splits one day’s serving into 2 capsules; it is not a double dose. Ritual Women 18+ and Thorne 2/Day are 2 capsules a day. Pick the one you will take every day.
Should I pick one with iron or without?
With iron only if you are a woman 19 to 50, the group that needs the most. Most others get enough from food (iron by age).
More multivitamin guides: Best overall · For women · For men · Tested · Thorne vs Ritual · Do you need one? · Third-party tested supplements
Sources
- NIH Office of Dietary Supplements: Multivitamin/mineral fact sheet (updated July 17, 2024); iron needs from the Iron fact sheet; upper limits from the Vitamin D, Iron, Zinc, Niacin, Vitamin B6 (including the 2023 European limit), Selenium, Vitamin A and Folate health professional fact sheets, read September 29 and October 1, 2026; child iron poisoning from the Iron fact sheet; iron in pregnancy (27 mg) from the Iron fact sheet. Iron warning: FDA, 21 CFR 101.17(e).
- US Preventive Services Task Force. Folic acid supplementation to prevent neural tube defects. JAMA. 2023. PubMed 37526713
- US Preventive Services Task Force. Vitamin, mineral, and multivitamin supplementation to prevent cardiovascular disease and cancer. JAMA. 2022. PubMed 35727271
- The Centrum Silver trials: Sesso HD, et al. Physicians’ Health Study II. JAMA. 2012. PubMed 23117775. Sesso HD, et al. COSMOS. Am J Clin Nutr. 2022. PubMed 35294969
- Labels: NIH Dietary Supplement Label Database, 179537, 331220, 331219, 278454, 323076.