The best vitamins to take depend on your age, diet, and life stage, but a few stand out as widely beneficial: vitamin D, magnesium, B12 (especially if you’re over 50 or eat plant-based), and folate for women who could become pregnant. Most people don’t need a cabinet full of supplements. A targeted approach based on common gaps in the modern diet will do more for you than a generic multivitamin.
Vitamin D: The Most Common Deficiency
Vitamin D tops nearly every expert’s shortlist because so many people fall short. Your body makes it from sunlight, but indoor lifestyles, sunscreen use, and living at northern latitudes all reduce production. You need it for calcium absorption, bone strength, immune function, and nerve signaling. Blood levels below 30 nmol/L (12 ng/mL) weaken bones and affect overall health, while levels of 50 nmol/L (20 ng/mL) or above are considered adequate. Anything above 125 nmol/L (50 ng/mL) is too high and can cause problems.
Adults under 70 need 600 IU per day, and those over 70 need 800 IU. The upper safe limit is 4,000 IU daily. Vitamin D is fat-soluble, so take it with a meal that includes some fat, even a small amount of yogurt or food cooked in oil. Without fat in your stomach, your body won’t absorb it well.
Magnesium: Picking the Right Form Matters
Magnesium supports hundreds of processes in your body, from muscle contraction to energy production to sleep quality. Many adults don’t get enough from food alone, and the form of supplement you choose makes a real difference.
Magnesium glycinate, which is bonded to an amino acid, is absorbed more efficiently and is gentler on the stomach. It’s a good choice if you’re taking it for sleep or general health. Magnesium citrate is also well absorbed but has a laxative effect, which can be a benefit if you deal with constipation or a drawback if you don’t. Magnesium oxide is the cheapest and most widely available option, but your body absorbs it less efficiently than chelated forms.
Vitamin B12: Essential for Plant-Based Eaters and Older Adults
B12 keeps your red blood cells and nerves healthy. The recommended intake is 2.4 micrograms per day for all adults, but two groups face a higher risk of deficiency. People who eat vegan or vegetarian diets get very little B12 from food, since it’s found almost exclusively in animal products. A daily supplement of 4 to 7 micrograms is generally recommended for those on plant-based diets.
Older adults face a different problem. Even if they eat meat, many lose the ability to efficiently absorb B12 from food as they age. Stomach acid production declines, and acid reflux medications make absorption worse. For adults over 65, a B12 supplement or fortified foods like cereals can bridge that gap without needing to change the diet itself.
Folate: Critical Before and During Pregnancy
The CDC recommends that all women capable of becoming pregnant get 400 micrograms of folic acid every day. This B vitamin prevents neural tube defects, which develop in the earliest weeks of pregnancy, often before a woman knows she’s pregnant. That’s why the recommendation applies broadly, not just to women actively trying to conceive.
Women who have had a previous pregnancy affected by a neural tube defect need a much higher dose of 4,000 micrograms daily, starting one month before conception and continuing through the first trimester. Folic acid is water-soluble, so it’s best taken on an empty stomach with a glass of water.
Calcium: Needs Increase With Age
Calcium works alongside vitamin D to maintain bone density. For most adults aged 19 to 50, 1,000 milligrams per day (from food and supplements combined) is sufficient. After 50, women’s needs increase to 1,200 milligrams. Men need 1,000 milligrams until age 70, then 1,200 milligrams, with an upper limit of 2,000 milligrams daily. If you eat dairy, leafy greens, and fortified foods regularly, you may already be close to your target. Supplementing makes the most sense if your diet consistently falls short.
Zinc: A Small Amount Goes a Long Way
Zinc supports immune function, wound healing, and cell growth. Adult men need 11 milligrams per day. Early research suggests it may also play a role in sperm quality, though that evidence is still developing. Most people who eat a varied diet with meat, shellfish, or legumes get enough zinc without supplementing, but vegetarians and vegans may fall short since plant-based zinc is harder for the body to absorb.
What the Latest Dietary Guidelines Emphasize
The most recent federal dietary guidelines shift the focus toward getting nutrients from whole foods rather than supplements. The guidelines prioritize high-quality protein at every meal (including eggs, poultry, seafood, red meat, beans, lentils, nuts, and seeds), healthy fats from whole food sources like olive oil, avocados, and full-fat dairy, and fiber-rich whole grains. They explicitly call for avoiding highly processed packaged foods, sugar-sweetened beverages, and refined carbohydrates like white bread and crackers.
The practical takeaway: supplements work best as a safety net for specific gaps, not as a replacement for eating well. A diet built around whole, minimally processed foods covers most of your vitamin and mineral needs on its own.
Fat-Soluble vs. Water-Soluble: When to Take Them
How you take a vitamin affects how much your body actually absorbs. Vitamins A, D, E, and K are all fat-soluble, meaning they need dietary fat to be absorbed properly. Take them with a meal that contains some fat.
Vitamins C and B12 are water-soluble and absorb best on an empty stomach with a glass of water. This creates a dilemma with multivitamins: taking one with food helps the fat-soluble vitamins but reduces absorption of the water-soluble ones, and vice versa. If you take a multivitamin, taking it with food is generally the better compromise, since the fat-soluble vitamins are harder to absorb otherwise.
Upper Limits and Safety
More is not better with vitamins, particularly fat-soluble ones that accumulate in your body rather than being flushed out in urine. Vitamin A has an upper limit of 3,000 micrograms (about 10,000 IU) per day for adults, and exceeding that over time can cause liver damage. Vitamin D tops out at 4,000 IU daily. Vitamin E’s safe upper limit is 1,000 milligrams per day from supplements.
Water-soluble vitamins are generally safer in higher doses because your kidneys excrete the excess, but there are still limits. Vitamin C caps at 2,000 milligrams, vitamin B6 at 100 milligrams, and folic acid at 1,000 micrograms. Taking a single supplement at its recommended dose is unlikely to cause problems, but stacking multiple products that contain the same vitamins can push you past safe thresholds without you realizing it. Check the labels of everything you take to avoid overlap.