Vitamins and Supplements: How to Choose Wisely

Medically Reviewed by Jabeen Begum, MD on August 02, 2023
7 min read

Vitamins are nutrients your body needs in small amounts to stay healthy. Supplements are pills, liquids, or powders that contain vitamins, minerals, or a combination of both, which some people use to fill in the blanks in their diets. Scientists don't know whether daily multivitamins stave off diseases, but many people take them to maintain or boost their health. Others take just one vitamin or mineral, such as iron, to make up for a shortage in their diets.

Before you add a supplement or vitamin to your routine, go over these questions with your doctor, pharmacist, or registered dietitian:

  • Can this supplement help me? Do I need it for a medical condition or to prevent disease?
  • What does the research say about its benefits?
  • How much should I take?
  • When and for how long do I need it?
  • Should I take it as a pill, powder, or liquid?
  • Which form of the vitamin (vitamin D2 or D3, for instance) is the best?
  • Are there any side effects?
  • What are the best brands of this supplement in terms of quality, safety, and how well they work?
  • Can I take it along with my other medications? Should I avoid any foods?
  • Will I need to stop taking it if I have to have surgery?

Vitamins and supplements come in many forms, including pills, liquids, or powders. The form you choose depends on how they work in your body and how you prefer to take them.

For example, some only work in a dry extract form, such as a capsule or pill. Others work faster and are more effective as a liquid. Some people need to take a liquid if they have trouble absorbing vitamins from a pill, or even if it’s hard for them to swallow capsules or tablets. Ask your pharmacist or doctor if you're confused about the right form to take.

Not all forms of a nutrient are the same. For example, vitamin D supplements can be either vitamin D2 or vitamin D3. Also, there are several types of vitamin E. When in doubt, talk with your doctor about which supplement suits your needs.

Supplements are not regulated by the FDA in the same way that drugs are. The FDA doesn't review these supplements for safety or efficacy before they hit the market.

The bottom line: Do your research and be careful when you’re shopping for new products. Other ways to stay safe:

  • If you eat a balanced diet rich in whole grains, fruits, and vegetables, you likely don't need to take a multivitamin. Talk to your doctor to see if you need any specific vitamins if you have a restricted diet.
  • Although these nutrients are essential to our bodies, some can be harmful in high doses. It’s especially important to avoid getting too much of vitamins A, D, E, and K because these build up in your body and can become toxic.


Supplements are not a good idea for people with some kinds of health conditions. They also can keep some medications from working as well as they should. Always talk with your doctor before you add any to your diet.

People who should avoid certain types of supplements include:

  • Those who are pregnant or breastfeeding. Some supplements can be dangerous to the fetus. A daily prenatal vitamin has the right types and amounts of nutrients for pregnancy and nursing.
  • Those who take heart medications, diuretics, blood thinners, aspirin, drugs that turn down the immune system, and steroids. With any type of drug, there’s always a chance that it won’t mix well with a supplement, but the problems can be especially severe with some of these drugs.
  • Those who are going to have surgery, because some products may lead to bleeding and other dangerous complications.
  • Those who’ve had cancer or are getting treated for it. Some supplements could help cancer cells grow or make treatments for the disease less effective.

When you’re ready to purchase supplements, keep these tips in mind:

  • Look for evidence about how well the product works in scientific studies from credible publications. Search for such studies in the National Institutes of Health (NIH) PubMed database: and the National Institute of Health - Office of Dietary Supplements. You can also call the manufacturer and ask which published studies they have to back up their claims. It’s also a good idea to find out how they ensure the ingredients listed on the supplement label are actually in the bottle.
  • If a product claims it will “cure” a disease, is “all-natural,” or has a “money-back guarantee,” be careful. Any supplement that sounds too good to be true likely is.
  • Choose brands labeled with the NSF International, US Pharmacopeia, Underwriters Laboratory, or Consumer Lab seal. These verify that the product actually contains the ingredients that the label says it does, and that the product doesn’t have any potentially harmful ingredients.
  • Be wary of supplements made outside the U.S., as many aren’t regulated, and some may have toxic ingredients.

Supplements don’t last forever, and they need a little care to keep them working well. After you buy them:

  • Keep them in a dark, cool, dry place. Avoid bathrooms and other damp spots.
  • Make sure you keep them on a high shelf or in a locked cabinet, out of children’s reach.
  • Some vitamins and supplements wear out when they sit on the shelf for too long. Do a regular check of your stash and throw out any that are past their expiration date.

Finally, always let your doctor know about any vitamins or supplements you plan to take, especially if you have a health condition or are on regular medication. Not all products work well for everyone, and some can be dangerous.

Here are some terms related to vitamins and supplements, which may be helpful to know:

Antioxidants. Substances such as vitamins A, C, E, and beta-carotene protect your body from the damage of oxidation caused by harmful molecules called free radicals.

Botanicals. These substances are obtained from plants and used in food supplements, personal care products, or pharmaceuticals. Other names include “herbal medicine” and “plant medicine.”

Daily value. Found on food and drink nutrition labels, this number tells you the percentage of the recommended dietary allowance provided by one serving of the food or drink in question.

Fat-soluble vitamins. The fat-soluble vitamins are A, D, E, and K. Your body stores excess fat-soluble vitamins in your liver and body fat, then uses them as needed. Ingesting more fat-soluble vitamins than you need can be toxic, causing side effects such as nausea, vomiting, and liver and heart problems depending on the vitamin.

Fortify. To increase a food or drink's nutritional value by adding vitamins, minerals, or other substances. For example, milk is fortified with vitamins A and D.

Free radicals. An atom or molecule with at least one unpaired electron, making it unstable and reactive. When free radicals react with certain chemicals in the body, they may interfere with the ability of cells to function normally. Antioxidants can stabilize free radicals.

Herbs. Herbs are plants used as flavorings and spices in cooking, but herbs can also be used as supplements for health or medicinal reasons.

Megadose. Supplements that provide more than 100% of the daily value of the body's required vitamins and minerals.

Micronutrients. The name given to certain vitamins and minerals that your body needs only in small amounts. Micronutrients are vital to your body's ability to process the macronutrients,” which include fats, proteins, and carbohydrates. Examples of micronutrients are chromium, zinc, and selenium.

Minerals. Nutrients found in the earth or water and absorbed by plants and animals for proper nutrition. Minerals are the main component of teeth and bones and help build cells and support nerve impulses, among other things. Examples include calcium and magnesium.

Multivitamin. A pill, beverage, or other substance containing more than one vitamin.

Oxidation. A chemical reaction in which oxygen combines with a substance, changing or destroying its normal function. Oxidation can damage cell membranes and interfere with a cell's regulatory systems, but it is also part of our normal-functioning immune system.

Phytochemicals. Compounds found in fruits, vegetables, and other plants that can protect your health. Phytochemicals (sometimes called phytonutrients) include beta-carotene, lycopene, and resveratrol.

Prenatal vitamins. Specially formulated multivitamins that ensure a pregnant woman gets enough essential micronutrients. Prenatal supplements generally contain more folic acid, iron, and calcium than standard adult supplements.

Recommended Dietary Allowance (RDA). The amount of nutrients needed daily to prevent the development of disease in most people. An example is vitamin C; the RDA ranges from 40-120 milligrams depending on age and sex.

Supplements. These include vitamins, minerals, herbs, or other substances, which are taken orally and meant to correct deficiencies in the diet.

U.S. Pharmacopeia (USP). A nonprofit authority that sets standards and certifies supplements that meet certain quality, strength, and purity standards, some of which are called the Good Manufacturing Practices (GMP). Many supplements carry the USP symbol on their label.

Vitamins. Naturally found in plants and animals, vitamins are vital to growth, energy, and nerve function. There are two types of vitamins used by the body to support health: fat-soluble and water-soluble.

Water-soluble vitamins. Water-soluble vitamins such as B-6, C, and folic acid are easily absorbed by the body. Your body uses the vitamins it needs and then excretes excess water-soluble vitamins in urine. Because excess amounts of these vitamins are not stored in the body, there is less risk of toxicity than with fat-soluble vitamins but a greater risk of deficiency.