Supplement guide
How to Read a Supplement Facts Panel
A plain-language breakdown of every element on a dietary supplement label, from serving sizes and Daily Values to proprietary blends and inactive ingredients.
Key Takeaway
Supplement Facts panels are regulated by FDA but differ significantly from food Nutrition Facts. The most important things to check: serving size (affects all amounts), whether ingredients are fully disclosed or hidden in a proprietary blend, and the %DV relative to your actual needs. The NIH DSLD records standardized label data for over 113,000 products, making it possible to compare disclosures across brands side by side.
The Basic Structure of a Supplement Facts Panel
Every dietary supplement sold in the United States must display a Supplement Facts panel under FDA regulations (21 CFR 101.36). The panel is divided into three main zones: the serving information at the top, the active ingredient table in the middle, and the "Other Ingredients" declaration at the bottom.
The serving information tells you how many servings are in the container and what one serving consists of (e.g., "2 capsules"). This is the foundation for interpreting every number that follows, all amounts are per serving, not per capsule or per gram, unless otherwise stated.
Reading the Active Ingredient Table
The main table lists each active ingredient with three pieces of information:
- Ingredient name: May include the chemical form (e.g., "Magnesium as magnesium citrate"), which affects bioavailability.
- Amount per serving: Listed in milligrams (mg), micrograms (mcg/µg), international units (IU), colony-forming units (CFU for probiotics), or other appropriate units.
- % Daily Value (%DV): The percentage of the FDA's reference daily intake provided by one serving. An asterisk (*) means no daily value has been established for that ingredient.
You can browse the ingredient database to see how commonly each ingredient appears across products, and the typical dose range found in the DSLD data.
Supplement Facts vs. Nutrition Facts: Key Differences
These two panels look similar but serve different regulatory purposes:
- Label name: "Supplement Facts" (supplements) vs. "Nutrition Facts" (foods). The title is legally mandated based on product category.
- Calorie disclosure: Required on food labels. Optional on supplement labels unless the product provides significant calories.
- Ingredient source: Supplement panels may note the plant part or source (e.g., "Elderberry extract [fruit]"), which food labels do not require.
- %DV reference: Both use FDA daily values, but supplements may list nutrients not tracked in food labels (e.g., specific botanical compounds).
- Pre-market review: Food additives require safety approval. Supplement ingredients introduced before 1994 were grandfathered; new dietary ingredients (NDIs) introduced after require an FDA notification.
Understanding Proprietary Blends
A proprietary blend allows a manufacturer to list a group of ingredients under a single branded name (like "Neuro Complex" or "Antioxidant Fusion") while only disclosing the total weight of the blend, not the individual amounts. This is legal under FDA rules but limits your ability to verify dosing.
The NIH DSLD records blend names and total weights for products that use them. When using PlainVitamins to compare supplements, products with fully disclosed individual ingredient amounts are generally easier to evaluate than those relying on proprietary blends.
The "Other Ingredients" Section
Everything below the active ingredient table is listed as "Other Ingredients", the non-active components used in manufacturing. Common examples include:
- Capsule materials: Gelatin (animal-derived) or hypromellose (vegetarian/vegan)
- Flow agents: Magnesium stearate, silicon dioxide, help capsules fill evenly
- Fillers: Microcrystalline cellulose, rice bran, dicalcium phosphate
- Coatings: Carnauba wax, shellac, used on tablets
If you have specific dietary restrictions (vegan, gluten-free, soy-free), this section requires careful review. The DSLD data recorded by NIH includes other ingredient lists, which are searchable through the brand pages on PlainVitamins.
Frequently Asked Questions
What does "% Daily Value" mean on a supplement label?
Percent Daily Value (%DV) tells you how much of a nutrient a single serving provides relative to the recommended daily intake for an average adult eating 2,000 calories per day. A %DV of 100% means one serving supplies the full daily reference amount. Values above 100% are common in supplements, for example, many vitamin B12 products list 1,000% or more. These reference values, set by FDA, are a general guide and not personalized recommendations.
How is a Supplement Facts panel different from a Nutrition Facts panel?
Supplement Facts panels (required on dietary supplements) list active ingredients with their amounts per serving and %DV, plus other ingredients (inactive excipients, binders, fillers). Nutrition Facts panels (required on food) include calories, macronutrients, and selected micronutrients. Supplement panels are not required to list calories unless the product contains a meaningful caloric contribution. The serving size unit also differs, supplements often use "capsules" or "tablets" while foods use grams or milliliters.
What does "Other Ingredients" mean on a supplement label?
"Other Ingredients" lists inactive components, binders, fillers, flow agents, coating materials, flavors, and preservatives used in manufacturing. Examples include magnesium stearate (flow agent), silicon dioxide (anti-caking), hypromellose (capsule shell), rice bran (filler), and natural flavors. These ingredients are generally recognized as safe (GRAS) at the amounts used, but consumers with specific allergies or sensitivities should review this section carefully.
What does "proprietary blend" mean and why is it a concern?
A proprietary blend is a mixture of ingredients listed as a group under one name (e.g., "Energy Matrix") with only the total blend weight disclosed, not the individual amounts of each ingredient inside the blend. This means you cannot verify how much of each active ingredient you are actually getting. The NIH DSLD records whether products use proprietary blends. When comparing products, those with fully disclosed ingredient amounts are easier to evaluate.
What does "Serving Size" mean and why does it matter?
Serving size is the manufacturer-defined unit for which all nutrient amounts and %DVs are calculated. It can be 1 capsule, 2 tablets, 1 scoop, or any other amount. Always check the serving size before comparing two products, a product with 500 mg of vitamin C per 2 capsules has the same dose as one with 250 mg per 1 capsule, but the per-serving numbers look different. Larger serving sizes also affect cost-per-dose calculations.
What does "not evaluated by the FDA" mean on supplement labels?
The standard disclaimer, "These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease", is legally required on all supplements making structure/function claims. It signals that the manufacturer has not submitted clinical evidence to the FDA proving the product does what it claims. Unlike prescription drugs, supplements do not require FDA approval for efficacy before going to market.
Sources
- NIH Office of Dietary Supplements, Dietary Supplement Label Database (DSLD)
- FDA, 21 CFR Part 101.36: Nutrition labeling of dietary supplements
- FDA, Dietary Supplements: What You Need to Know (fda.gov)
- NIH ODS, Dietary Supplement Fact Sheets (ods.od.nih.gov)
This content is for informational purposes only and does not constitute medical advice. Consult a healthcare provider before starting any supplement.
Understanding the Data
The information presented throughout this guide is informed by publicly available public records published by federal and state government agencies. Our database aggregates and standardizes these records to make them more accessible and easier to interpret for general audiences. When we reference specific statistics or trends, they are drawn directly from these authoritative sources unless explicitly noted otherwise.
It is important to understand the limitations of any large-scale data dataset. Records may contain errors from the original data collection process, some fields may be incomplete for older entries, and classification systems may have changed over time. Our analysis accounts for these factors by clearly labeling data vintage, flagging records with missing critical fields, and noting when temporal comparisons span methodology changes in the source data.
For readers who want to conduct their own research, we recommend going directly to the source whenever possible. federal and state government agencies provides detailed documentation on collection methodology, sampling frames, and known data quality issues. Our goal is not to replace primary sources but to make them more approachable and to highlight patterns that may not be immediately obvious when browsing raw records.
How We Analyze Data Records
Our analytical approach involves several steps designed to surface meaningful insights from large datasets. First, we clean and standardize the raw data, handling variations in naming conventions, date formats, and categorical labels. Then we compute summary statistics, distributions, and comparative benchmarks across relevant dimensions such as geography, time period, and category type.
Key metrics we examine include statistical records, geographic distributions, temporal trends. These indicators provide a multi-dimensional view of each entity in our database, allowing users to understand not just individual records but how they compare to peers, regional averages, and national benchmarks. We believe this contextual approach is far more valuable than presenting raw numbers in isolation.
