Comparing Supplement Labels: Amounts, Serving Size, Testing, Added Ingredients and Cost Per Serving
How to compare two supplement labels: serving size, amounts, percent Daily Value, testing seals, added ingredients, proprietary blends and cost per serving, with what research found.
Content last updated . This page has not been medically reviewed.
The question: how do you compare two supplement labels, and which costs less for the same amount?
This page walks through the US Supplement Facts label in the order that avoids common mistakes. It does not rank brands or tell you what to buy. Other countries' labels differ. See also reading supplement labels.What each label element is, and what is documented
| Label element | What it is | What is documented | Evidence strength | Caution |
|---|---|---|---|---|
| Serving size | Unit the amounts refer to | A serving can be several units, such as "Amount Per 2 Tablets." [1] | FDA guidance (2005, nonbinding) | Compare per serving, not per bottle |
| Nutrient and source | The nutrient amount and its form | Sources may appear in the panel, e.g. "Calcium (as calcium carbonate)." [2] | FDA guidance | Different forms are not interchangeable; see calcium carbonate vs citrate |
| % Daily Value | Share of a label reference amount | FDA: 5% DV or less is low, 20% DV or more is high. [3] | FDA, US labels | A label reference, not a personal need; see RDA, AI, DV and UL |
| Other ingredients | Everything outside the panel | Listed in descending order by weight under "Other Ingredients." [2] | FDA guidance | Check allergens and sugars |
| Proprietary blend | Several ingredients under one weight | Only the total blend weight is listed. [1] | FDA guidance | Amounts cannot be compared with a plain product |
| Claims | Structure/function wording | Must carry the statement that it has not been evaluated by FDA. [4] | FDA guidance | A claim is not proof it works |
Higher is not automatically better: compare amounts with upper limits, not only the Daily Value.
Do label amounts match the bottle?
Not always. Overages are common: many ingredients are added above the declared amount, and overages are not standardized between makers. [5] In adult multivitamin-minerals, measured content exceeded label amounts for all ingredients except thiamin, by about 1.5 to 13% for many nutrients and about 25% for selenium and iodine. [6] Other analyses found worse: only 13 of 30 immune-support products had accurate labels, and 36 of 44 weight-loss products (82%) had inaccurate labels, with no third-party seal on either group. [7][8] These were particular, non-random samples, so they are warnings, not market averages.Testing and seals
NCCIH says a manufacturer's use of "standardized," "verified" or "certified" does not necessarily guarantee quality or consistency. [9] A review for athletes lists choosing products verified by a third-party certification program as one safeguard. [10] What programs test is on quality testing and certifications. A seal speaks to the product, not to whether the ingredient helps you. NCCIH also notes products on the shelf may differ from those tested in studies. [9]Cost per serving
Proper evidence not found from research on cost comparisons across supplements; we searched PubMed for supplement cost-per-serving studies. This is arithmetic:- Divide the price by the number of servings in the container, not the number of capsules.
- Divide by the amount of the nutrient in a serving to get cost per unit of the nutrient.
- Compare only the same ingredient, same form and comparable amounts.
One indirect example: a systematic review of creatine trials reported that, in its marketplace review, monohydrate was the lowest-cost form, though prices change. [11] Cheapest is not necessarily right if the label is unreliable. See how to evaluate a supplement formula.
No universal winner
No label feature (a seal, a low price, a high %DV) makes one product right for everyone. The match between the exact ingredient, form and amount and a person's situation is a conversation for a clinician or pharmacist.Frequently asked questions
Does a third-party seal mean a supplement works?
No. A seal speaks to the product, not effectiveness. NCCIH says terms like "verified" do not necessarily guarantee quality. [9]
Why does serving size matter?
A serving can be several tablets, so two products with the same amount per serving may need different numbers of units. [1]
Is the cheapest supplement the best value?
Only if label amounts are accurate and the form is equivalent. Compare cost per amount of the nutrient, not per bottle.
What does 20% DV mean?
FDA considers 20% DV or more of a nutrient per serving high and 5% or less low. [3] It is a label reference, not a personal requirement.
What is a proprietary blend?
A group of ingredients listed with one total weight; individual amounts are not shown. [1]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety: ask a clinician or pharmacist
Tell your clinician or pharmacist about everything you take, especially if you are pregnant or breastfeeding, give supplements to a child, have kidney or liver conditions, take prescribed medicines or face surgery. Many supplements have not been tested in pregnant women, nursing mothers or children. [9] See how interactions work and product quality and contamination. Duplicated ingredients across products can add up: amounts and duplicate ingredients.
References
- U.S. Food and Drug Administration. Dietary Supplement Labeling Guide: Chapter IV. Nutrition Labeling. Nonbinding guidance (2005). Read 2026-10-22.
- U.S. Food and Drug Administration. Dietary Supplement Labeling Guide: Chapter V. Ingredient Labeling. Nonbinding guidance (2005). Read 2026-10-22.
- U.S. Food and Drug Administration. Daily Value on the Nutrition and Supplement Facts Labels. Content current as of 03/05/2024. Read 2026-10-22.
- U.S. Food and Drug Administration. Dietary Supplement Labeling Guide: Chapter VI. Claims. Nonbinding guidance (2005). Read 2026-10-22.
- Andrews KW et al. Dietary Supplement Ingredient Database (DSID) and the Application of Analytically Based Estimates of Ingredient Amount to Generate Further Nutrient Intake Estimates. J Nutr 2018. PMID 31505677. Read 2026-10-22.
- Andrews KW et al. Analytical ingredient content and variability of adult multivitamin/mineral products: national estimates for the Dietary Supplement Ingredient Database. Am J Clin Nutr 2017. PMID 27974309. Read 2026-10-22.
- Crawford C et al. Analysis of Select Dietary Supplement Products Marketed to Support or Boost the Immune System. JAMA Netw Open 2022. PMID 35947382. Read 2026-10-22.
- Crawford C et al. Label Accuracy and Quality of Select Weight-Loss Dietary Supplements Sold on or near US Military Bases. Nutrients 2024. PMID 39770990. Read 2026-10-22.
- National Center for Complementary and Integrative Health (NIH). Using Dietary Supplements Wisely. Read 2026-10-22.
- Jagim AR et al. Prevalence of adulteration in dietary supplements and recommendations for safe supplement practices in sport. Front Sports Act Living 2023. PMID 37841887. Read 2026-10-22.
- Fazio C, Elder CL, Harris MM. Efficacy of Alternative Forms of Creatine Supplementation on Improving Performance and Body Composition in Healthy Subjects: A Systematic Review. J Strength Cond Res 2022. PMID 36000773. Read 2026-10-22.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.