Choosing Supplements

What to look for when comparing ingredients and doses.

Two bottles can both say “1,000 mg” and contain very different amounts of the ingredient you’re looking for. One may list the amount in a single capsule, while the other lists it for two. A third may put the same number on the front for a blend of several ingredients. The Supplement Facts panel is where you can start to tell them apart.

1. Start with a reason

Before you compare brands, write down what you want the supplement to do. Filling a dietary gap, addressing a confirmed deficiency, and supporting a training goal are different reasons to buy. A clear goal helps you decide which ingredient matters and what evidence would be relevant.

If you’re considering a supplement because of ongoing symptoms, such as fatigue, ask a healthcare professional what might be causing them. If a clinician has identified a deficiency, use their dose and follow-up plan as your starting point. NIH guide to dietary supplements

2. Check the serving size before comparing numbers

Find the serving size at the top of the Supplement Facts panel. Then read the amount per serving and check how many servings the directions suggest. Compare products on the same basis, whether that’s one capsule, a labeled serving, or the amount you would actually take in a day.

Product A contains more per labeled serving. Product B contains more per capsule. Both comparisons are correct, but they answer different questions. Also check the units. A milligram (mg) equals 1,000 micrograms (mcg), so the same number can represent very different amounts. FDA dietary supplement labeling overview

3. Compare the ingredient and its form

Look for the specific ingredient name, its form, and the amount listed. With a mineral, compare the amount on the mineral’s own line in Supplement Facts. With an herbal product, check the plant name, plant part, and whether it’s a powder or an extract. If the label lists a standardized compound, note its percentage or amount. Two extracts with the same milligram number can differ in composition.

Fish oil is a good example. If a label lists 1,000 mg of fish oil, with 180 mg of EPA and 120 mg of DHA per serving, that serving contains 300 mg of EPA and DHA combined. If you’re shopping specifically for EPA and DHA, compare those amounts across labels. The fish oil total answers a different question. NIH omega-3 fact sheet

When a brand points to research, see whether the study used the same ingredient form, a comparable dose, and a group of people relevant to your goal. A study on one extract or dose may tell you little about another.

4. Put the dose in context

The Percent Daily Value (%DV) shows how much one serving contributes to an FDA labeling reference amount. It helps you compare products, but your individual needs can differ. A higher percentage alone tells you little about whether you need that amount.

Some nutrients also have a Tolerable Upper Intake Level (UL), which is the highest average daily intake likely to pose little risk for most people in a particular group. Which sources count toward the limit depends on the nutrient. Check the guidance for the specific nutrient before combining products, especially if you already take a multivitamin. NIH guide to supplement intake and safety

Check for overlap and interactions. Put your multivitamin, single-ingredient supplements, and fortified powders side by side. Add up repeated ingredients based on what you take each day. If you take medication, are pregnant or breastfeeding, or have surgery coming up, bring the labels to a healthcare professional or pharmacist.

5. Look inside proprietary blends

A U.S. label may list the total weight of a proprietary blend and name its ingredients without giving each ingredient’s individual amount. For example, “Focus Blend, 600 mg” across three ingredients gives you the blend total. It leaves the individual doses unknown. If you need to compare a particular ingredient with a study or another product, choose a label that discloses its amount. FDA Supplement Facts labeling guide

6. Check quality and read claims carefully

Look for a clearly identified manufacturer, contact information, and a lot number on the package. Independent verification programs, such as USP or NSF, can offer additional information about a product’s quality. Check the exact product in the certifier’s directory and read what the certification covers. A seal can help you assess quality. Evidence that the supplement will help with your specific goal is a separate question.

In the United States, the FDA generally does not approve dietary supplements for safety and effectiveness before they are sold. Be skeptical of claims that a supplement cures a disease or can replace a prescription. Also read the Other Ingredients list for potential allergens, sweeteners, or capsule materials that matter to you. FDA questions and answers on supplements · NIH overview of supplement quality

7. Compare cost per serving

A $24 bottle with 60 capsules sounds cheaper than a $30 bottle with 60 capsules. But if the first bottle requires two capsules per serving, it contains 30 servings at $0.80 per serving. If the second uses one capsule per serving, it contains 60 servings at $0.50 per serving. Once you’ve checked the ingredient, amount, and quality, cost per serving gives you a better basis for comparing prices.