Most people don’t need a cabinet full of supplements. Fewer than 10% of Americans have a true nutritional deficiency, according to CDC data, and the nutrients most commonly lacking are vitamin D, vitamin B6, and iron. The right supplements for you depend on your diet, age, life stage, and any medications you take. Here’s how to figure out what’s actually worth your money.
Start With What Most People Actually Lack
The three most common deficiencies in the U.S. population are vitamin D, vitamin B6, and iron. Vitamin D deficiency varies dramatically by race and ethnicity: about 31% of Black Americans and 12% of Mexican Americans are deficient, compared to 3% of white Americans. This is largely because darker skin produces less vitamin D from sunlight.
For most healthy adults under 75, the Endocrine Society recommends simply meeting the standard daily allowance of vitamin D (600 IU for adults under 70, 800 IU for those over 70) rather than taking mega-doses. Routine blood testing for vitamin D levels isn’t recommended for healthy people, since researchers haven’t been able to pin down a specific blood level that clearly prevents disease. If you do supplement, daily lower doses work better than taking a large weekly or monthly dose.
Iron is worth mentioning because it’s easy to over-supplement. Unless you have a diagnosed deficiency, heavy menstrual periods, or follow a plant-based diet, extra iron can do more harm than good. A standard multivitamin covers most people’s B6 needs.
Omega-3 Fatty Acids for Heart Health
Fish oil is one of the most popular supplements, and the evidence behind it is real but specific. If you already have heart disease, the American Heart Association recommends about 1 gram per day of EPA plus DHA (the two active components in fish oil), preferably from eating oily fish like salmon, mackerel, or sardines. For people with very high triglycerides, prescription-strength omega-3s at 4 grams per day can lower triglyceride levels significantly.
For healthy people without heart disease, the protective effect of omega-3 supplements is much weaker. Eating fish twice a week is generally enough. If you don’t eat fish at all, a supplement providing around 250 to 500 mg of combined EPA and DHA daily is a reasonable baseline. The FDA recommends that supplement labels not exceed 2 grams per day of EPA and DHA combined.
Magnesium: Pick the Right Form
Magnesium is involved in hundreds of processes in your body, from muscle function to sleep regulation. Many people fall short of the recommended intake through diet alone. But the type of magnesium you take matters more than most people realize.
Magnesium glycinate is the gentlest on your stomach and has a calming effect that may help with sleep and stress. Magnesium citrate absorbs well but can cause loose stools, which makes it a better choice if you also deal with constipation. Magnesium malate is easier to digest and is sometimes preferred by people looking for an energy-supporting form. Magnesium oxide, the cheapest and most common form in drugstore supplements, absorbs poorly compared to the others.
Creatine for Muscle and Aging
Creatine monohydrate isn’t just for bodybuilders. Research shows it increases lean muscle mass and strength in older adults when paired with resistance training, outperforming exercise alone. Your body uses roughly 2 grams of creatine per day to maintain normal levels, and you get some from meat, fish, and poultry. People who eat little or no meat, and adults over 50 who are losing muscle mass, tend to benefit most from supplementing with 3 to 5 grams per day.
Folic Acid During Pregnancy
If you’re pregnant or planning to become pregnant, folic acid is non-negotiable. It’s the only form of folate proven to prevent neural tube defects, which are serious birth defects of the brain and spine. The CDC recommends 400 micrograms daily, ideally starting at least one month before conception.
You may have seen methylfolate marketed as a superior alternative, especially for people with gene variants that affect folate metabolism. While methylfolate is a bioactive form of the vitamin, the clinical evidence for preventing birth defects specifically comes from folic acid. Since grain products in the U.S. have been fortified with folic acid, folate deficiency has dropped to less than 1% in women of childbearing age.
Pregnant women also benefit from omega-3s. Guidelines from several international health bodies recommend at least 250 mg of DHA plus EPA daily during pregnancy, with an additional 100 to 200 mg of DHA on top of that. Women with low DHA intake (under 150 mg per day) may benefit from 600 to 1,000 mg daily starting in the second trimester.
Fat-Soluble Vitamins and Toxicity Risk
Vitamins A, D, E, and K dissolve in fat and accumulate in your body, which means you can take too much. Vitamin D toxicity typically only occurs at doses above 10,000 IU per day, but when it happens, it forces calcium levels dangerously high. Symptoms include fatigue, confusion, muscle weakness, frequent urination, and excessive thirst. Over time, this can damage your kidneys, bones, and soft tissues.
The practical takeaway: more is not better with fat-soluble vitamins. Stick to recommended doses unless a healthcare provider has tested your levels and prescribed something higher.
Supplements That Interfere With Medications
If you take blood thinners or cholesterol-lowering statins, some common supplements can cause dangerous interactions. Garlic, ginkgo biloba, ginseng, evening primrose oil, and saw palmetto all increase bleeding risk when combined with blood thinners like warfarin. Coenzyme Q-10 and ginseng can reduce warfarin’s effectiveness, which is equally dangerous in the opposite direction.
St. John’s wort is one of the worst offenders. It interferes with blood thinners and reduces the effectiveness of several statins. It also interacts with antidepressants, birth control pills, and many other medications. If you take any prescription drugs, check for interactions before adding a new supplement.
How to Tell if a Supplement Is Worth Buying
The supplement industry in the U.S. is not regulated the way prescription drugs are. Products can contain less of an ingredient than the label claims, or be contaminated with substances not listed. Third-party certification is the closest thing to a quality guarantee. Look for seals from organizations like NSF International, USP, or Informed Sport on the label.
These programs go beyond simply testing the finished product. They audit the manufacturing process, verify that what’s on the label matches what’s in the bottle, and screen for contaminants. A certified supplement should come from a lab accredited to recognized international standards (ISO 17025) with testing protocols specific to dietary supplements. If a product doesn’t carry any third-party certification, that doesn’t mean it’s harmful, but it does mean no one outside the company has verified what’s inside.
A Practical Starting Point
For most healthy adults eating a reasonably varied diet, the shortlist is simple: vitamin D at the recommended daily allowance, magnesium if you’re not getting enough from food, and omega-3s if you rarely eat fish. Add creatine if you’re over 50 or exercise regularly. Add folic acid if pregnancy is a possibility. Everything else should be driven by a specific, identified need rather than a general sense that more supplements equal better health.