21 CFR 101.17 — Warning and Notice Statements on Food Labels
21 CFR 101.17 requires specific warning and notice statements on certain categories of food products. Unlike voluntary advisory statements ('keep out of reach of children'), these are mandatory — the exact required language must appear on the label. The most significant requirement for supplement brands is the iron warning, which applies to all iron-containing dietary supplements in solid oral dosage form regardless of the amount of iron per serving.
21 CFR 101.17 requires specific, mandatory warning and notice statements on certain categories of food and dietary supplement products. These are not advisory statements a brand may choose to include — they are required by law for the covered product categories, and failure to include them is a misbranding violation.
Iron-Containing Dietary Supplements
The Warning Requirement
Under 21 CFR 101.17(e), any dietary supplement in solid oral dosage form (e.g., tablets or capsules) that contains iron or iron salts for use as an iron source must bear the following warning statement:
WARNING: Accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under 6. Keep this product out of reach of children. In case of accidental overdose, call a doctor or poison control center immediately.
There is no minimum iron amount threshold — the warning applies to all iron-containing dietary supplements in solid oral dosage form regardless of the quantity of iron per serving.
Placement and Format
The warning must appear:
Prominently and conspicuously on the information panel of the immediate container label
Where the immediate container is not the retail package, also on the information panel of the retail package label
In conspicuous and legible type in contrast with the background
Set off in a box by use of hairlines
The word "WARNING" in all capitals
For unit-dose packaged supplements, the warning must appear on the immediate container labeling in a way that keeps the warning intact until all dosage units are used.
Who This Applies To
The requirement applies to any dietary supplement in solid oral dosage form (tablets, capsules, caplets) that contains iron for use as an iron source. It does not apply to liquid supplements or topical products.
Common supplement categories subject to this requirement:
Prenatal vitamins (typically 27–60 mg iron per serving)
Therapeutic iron supplements (e.g., ferrous sulfate 325 mg = 65 mg elemental iron)
High-potency multivitamins containing iron
Any other tablet or capsule supplement listing iron as an ingredient
Saccharin Warning
Under 21 CFR 101.17(a)–(d), foods containing saccharin must bear a warning about saccharin's potential health effects. Specifically, foods and beverages with saccharin must include:
Use of this product may be hazardous to your health. This product contains saccharin which has been determined to cause cancer in laboratory animals.
Note: The saccharin warning was required under the Saccharin Study and Labeling Act of 1977 and maintained through subsequent legislation. However, in 2000, the National Toxicology Program removed saccharin from its list of potential carcinogens following updated scientific review. Congressional action in 2000 removed the mandatory warning requirement for saccharin products. As of the current regulation, the saccharin warning under the original 21 CFR 101.17(a)–(d) framework has been superseded. Brands should verify the current status under the applicable federal legislation if their product contains saccharin.
Aspartame — Phenylalanine Notice
Under 21 CFR 101.17(f), foods and dietary supplements containing aspartame must include the following statement:
PHENYLKETONURICS: CONTAINS PHENYLALANINE
This notice is required because individuals with phenylketonuria (PKU) — a genetic metabolic disorder — cannot process phenylalanine, an amino acid component of aspartame. Failure to include this notice on aspartame-containing products is a misbranding violation that poses a direct health risk to a specific consumer population.
Placement
The phenylalanine notice must appear:
On the information panel or on the PDP
In conspicuous type in contrast to the background
The word "PHENYLKETONURICS" must appear in all capitals
Self-Rising Flour — Sodium Notice
Under 21 CFR 101.17(g), self-rising flour that is labeled as low sodium must bear a notice that it has been processed to reduce sodium. This is a narrow category-specific requirement applicable to baking ingredient products and is less relevant for supplement brands.
Dietary Supplements — Voluntary vs. Mandatory Warnings
It is important to distinguish the mandatory warnings under 21 CFR 101.17 from voluntary advisory statements many supplement brands include:
Statement Type | Example | Required? |
|---|---|---|
Iron warning (all iron-containing solid oral supplements) | "WARNING: Accidental overdose..." | Mandatory under 21 CFR 101.17(e) |
Phenylalanine notice (aspartame) | "PHENYLKETONURICS: CONTAINS PHENYLALANINE" | Mandatory under 21 CFR 101.17(f) |
Drug interaction advisory | "Consult your physician if taking medication" | Voluntary |
Pregnancy advisory | "Not recommended during pregnancy" | Voluntary (unless otherwise required) |
Prop 65 warning (California) | "WARNING: This product contains..." | Mandatory under California law |
Voluntary warnings are not regulated by 21 CFR 101.17, but they are subject to the general misbranding provisions — they cannot be false or misleading.
How Truli Helps with Warning Statement Compliance
Iron warning detection: Truli checks Supplement Facts panels for iron-containing solid oral dosage supplements and flags products that require the mandatory iron warning
Aspartame ingredient detection: Truli scans ingredient lists for aspartame and verifies the phenylalanine notice is present on the label
Warning placement verification: Truli confirms that the iron warning appears on the PDP (not just the information panel) in the required format
Format audit: Truli checks that "WARNING" appears in all capitals and bold type as required
Related Regulations
21 CFR Part 101 — FDA food labeling overview
21 CFR 101.36 — Supplement Facts Panel — Supplement Facts format where iron content is declared
FALCPA / FASTER Act Allergen Labeling — Other mandatory warning-type disclosures required by law
California Prop 65 — State-specific mandatory warning requirements
Frequently Asked Questions
My prenatal vitamin contains 27 mg of iron — do I need the warning?
Yes. 21 CFR 101.17(e) does not set a minimum iron amount — the warning is required for any dietary supplement in solid oral dosage form that contains iron or iron salts for use as an iron source, regardless of how many milligrams of iron are present per serving.
We use aspartame only as a trace ingredient. Does the phenylalanine notice still apply?
Yes. 21 CFR 101.17(f) does not set a threshold — any amount of aspartame in a food or supplement triggers the phenylalanine notice requirement. The health risk to PKU individuals exists regardless of the dose.
Can we combine the iron warning with other advisory text?
The mandatory iron warning text must appear exactly as required — it cannot be paraphrased or abbreviated. Additional advisory text may appear nearby, but the required language must be present verbatim. The word "WARNING" must appear in all capitals.
A note from Truli: Truli is not a law firm, and this article does not constitute or contain legal advice or create an attorney-client relationship. When determining your obligations and compliance with respect to relevant laws and regulations, you should consult a licensed attorney.
Last updated: April 2026. Reflects 21 CFR 101.17 as of April 2026. Book a demo to see how Truli monitors food label compliance.
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