How much of each vitamin and mineral do you need each day? This made-up multivitamin label shows what to aim for (from foods and supplements combined), according to the Daily Values (DVs) set by the Food and Drug Administration. The DVs are based on the Recommended Dietary Allowances (RDAs), which may vary by age and sex.

Vitamin A

Most multivitamins contain a mix of retinol (vitamin A) and beta-carotene (which our bodies convert to retinol). More than 3,000 micrograms (mcg) a day of retinol from supplements can cause birth defects if taken by pregnant people. High doses of beta-carotene (7,500 to 15,000 mcg of vitamin A a day) raise the risk of lung cancer in smokers and former smokers. (Note: Preservision AREDS Formula for macular degeneration has high a dose of beta-carotene. Preservision AREDS 2 Formulas do not.)

Thiamin (B-1), Riboflavin (B-2), Niacin (B-3), B-6

Way-above-the-DV doses (often added to “high potency B complex” vitamins) are useless but probably safe. Exceptions: levels over 35 milligrams of niacin from supplements can cause flushing of the skin and more than 100 mg of B-6 can cause (reversible) nerve damage and skin lesions.

Folate (Vitamin B-9)

The DV is 400 micrograms DFE (Dietary Folate Equivalents), but supplements list both “mcg DFE” and “mcg Folic Acid.” The DFE accounts for the body’s ability to absorb the folic acid that’s added to supplements and fortified foods better than the folate that occurs naturally in foods. Caution: Anyone who could become pregnant should take a supplement with 400 mcg of folic acid (680 mcg DFE) to reduce the risk of birth defects like spina bifida, which can occur before you know you’re pregnant. If a multi has 100% of the DV, that’s 240 mcg of folic acid, so it’s not enough.

Vitamin B-12

Adults over 50 should get most of the DV (2.4 mcg) from a supplement or fortified foods because they may not make enough stomach acid to digest and absorb the B-12 that occurs naturally in meat, eggs, and dairy. People who take acid blockers or metformin or who eat no animal foods may also have low levels. A B-12 deficiency can cause irreversible nerve damage that can masquerade as dementia.

Biotin, Pantothenic Acid

They're superfluous. We get plenty from our food. The only way to run short on biotin is to keep eating large quantities of raw eggs, which contain a protein that binds biotin. Don’t expect extra biotin to do anything for your hair, skin, or nails.

Vitamin C

Many Americans get too little vitamin C from their food. The DV is 90 mg, but smokers need 125 mg a day because smoking creates extra cell-damaging free radicals. Taking more than 1,000 mg a day may cause kidney stones in men, and more than 2,000 mg a day may cause diarrhea in men and women.

Vitamin D

The DV is 800 IU (20 mcg). Our bodies make vitamin D from sunlight, and modest doses (typically 10 to 25 percent of the DV) are added to milk and a handful of plant milks, cereals, and yogurts. So taking a multi is the easiest way to get the DV. In a large trial, 2,000 IU (50 mcg) of vitamin D a day didn’t prevent cancer, heart disease, stroke, fractures, memory loss, frailty, or depression. More than 4,000 IU (100 mcg) a day may lead to dangerously high blood levels of calcium.

Vitamin E

The DV is 15 mg (22.4 IU). High doses of vitamin E may not be safe. In one large trial, men who took 400 IU a day for 5½ years had a 17 percent higher risk of prostate cancer. In another trial, men who took 400 IU every other day had a 74 percent higher risk of hemorrhagic stroke. To play it safe, look for a multi with no more than 60 IU. Good food sources include nuts, oils, and leafy greens.

Vitamin K

Most multivitamins have less than the DV (120 mcg) because vitamin K can interfere with blood-thinning drugs like warfarin (Coumadin). If you’re taking a blood thinner, check with your doctor about adjusting the dose before you start (or stop) taking a multivitamin that contains vitamin K. Leafy greens are the best food source.

Calcium 

The DV (1,300 mg) is based on what children aged 9 to 18 need. Men and premenopausal women up to age 70 need 1,000 mg. Men and postmenopausal women over 70 need 1,200 mg. Many multivitamins have 200 to 300 mg. (Some have far less.) That may be enough to get you to the DV, since each serving of milk, yogurt, cheese, or fortified food has 150 to 300 mg, and most people get around 250 mg from the rest of their diet. Taking a daily supplement with 1,000 mg or more may raise the risk of kidney stones.

Choline

Pregnant people need 450 milligrams a day, but even prenatal multivitamins typically supply little or none. (Some brands sell a choline capsule plus a prenatal multi.)

Chromium

The DV is 35 mcg. If you have type 2 diabetes, don’t expect chromium to lower your blood sugar or boost your metabolism.

Iodine

The Centers for Disease Control and Prevention warns that many women in their 20s and 30s may not get enough iodine, which the developing brain needs during pregnancy. Milk, yogurt, seafood, and multivitamins are good sources.

Iron

Premenopausal women, who lose iron through menstruation, should get the DV (18 milligrams). Men and postmenopausal women need only 8 mg. More isn’t better because there’s no easy way to know if you have genes that lead your body to store excess iron (hemochromatosis), which may raise your risk of cirrhosis, liver cancer, or diabetes.

Magnesium

Most people in the U.S. get less than the DV (420 mg), which may raise their risk of type 2 diabetes. Leafy greens, beans, whole grains, and nuts are the best sources. Few multis have room for more than 100 mg. Many have less. More than 350 mg of magnesium from supplements (but not foods) can cause diarrhea and stomach cramps.

Manganese, Molybdenum, Chloride, Boron

We get plenty of the other four minerals from our food.

Phosphorus

The DV is 1,250 mg. Most people get plenty from meat, poultry, grains, dairy, and the phosphate additives in processed foods. Too much phosphorus may raise the risk of heart and kidney disease. Look for a multi with little or none.

Potassium

The DV (4,700 mg) is outdated. The most up-to-date recommended intakes are 3,400 mg for men and 2,600 mg for women. Potassium can help lower blood pressure, but a typical multi has only 80 mg. Your best sources: fruits and vegetables.

Selenium

We average about 100 micrograms a day from our food. (The DV is 55 mcg.) Taking 200 mcg a day was linked to a higher risk of high-grade prostate cancer in men with high selenium levels, so stick to a multi with around 55 mcg or less.

Zinc, Copper

The DV for zinc is 11 mg and the DV for copper is 0.9 mg. Too much zinc (more than 40 mg from food and supplements combined) can make it harder to absorb copper.