FDA & Compliance

FDA Warning Letters for Supplements: Common Violations and How to Avoid Them

The FDA issues hundreds of warning letters to dietary supplement companies every year. These letters are published on the FDA's website, indexed by Google, and permanently associated with your brand name. Beyond the reputational damage, warning letters can lead to product seizures, injunctions, and even criminal prosecution in extreme cases. Understanding the most common violations is the first step to avoiding them.

Violation #1: Illegal Disease Claims

The single most common reason supplements receive warning letters. A dietary supplement cannot claim to diagnose, treat, cure, mitigate, or prevent any disease. The line between a legal structure/function claim and an illegal disease claim can be razor-thin:

• Legal: "Supports healthy blood sugar levels already within normal range"
• Illegal: "Lowers blood sugar" or "Helps manage diabetes"
• Legal: "Supports joint comfort and flexibility"
• Illegal: "Reduces arthritis pain" or "Anti-inflammatory"
• Legal: "Supports a healthy immune system"
• Illegal: "Prevents colds and flu" or "Boosts immunity to fight infections"

Disease claims are not limited to your label. The FDA also monitors websites, social media, Amazon listings, influencer posts, and even customer testimonials that you feature. If a customer review on your website says "This cured my migraines," and you leave it published, the FDA considers that an implicit claim by your brand.

For a deeper dive on navigating claims, see our guide on what you can and cannot say on your supplement label.

Violation #2: cGMP (Current Good Manufacturing Practices) Failures

21 CFR Part 111 requires all supplement manufacturers to follow cGMP. When the FDA inspects a manufacturing facility and finds violations, the warning letter goes to the manufacturer — but it can also implicate brands that use that facility. Common cGMP violations include:

• Failure to establish product specifications — no written specifications for identity, purity, strength, and composition
• Failure to test incoming raw materials — accepting ingredients without identity testing
• Inadequate batch records — incomplete documentation of manufacturing steps, equipment used, and quality checks
• Failure to investigate out-of-specification results — when a test fails, there must be a documented investigation and corrective action
• Inadequate cleaning and sanitation procedures — cross-contamination risk between products

As a brand owner, you are responsible for ensuring your contract manufacturer is cGMP compliant. Request their most recent FDA inspection report (Form 483) and ask how they addressed any observations. Work with manufacturers who undergo voluntary third-party GMP audits (NSF or NPA).

Violation #3: Labeling Errors

Beyond disease claims, labeling violations include:

• Missing or non-compliant Supplement Facts panel
• Missing the required FDA disclaimer for structure/function claims
• Failing to list all ingredients in the "Other Ingredients" section
• Missing allergen declarations
• Incorrect net quantity statement (wrong units or not in the principal display panel)
• Missing manufacturer or distributor name and address
• Using "Nutrition Facts" instead of "Supplement Facts"

Violation #4: New Dietary Ingredient (NDI) Issues

If your product contains a dietary ingredient that was not marketed in the U.S. before October 15, 1994, it may be classified as a New Dietary Ingredient (NDI). NDIs require a pre-market notification to the FDA at least 75 days before marketing, along with safety data. Selling a product containing an NDI without proper notification is a violation that can result in a warning letter and forced market withdrawal.

Common categories where NDI questions arise: novel botanicals from non-Western traditions, synthetic versions of naturally occurring compounds, and ingredients produced through new extraction or processing methods.

Violation #5: Adulterated Products

A supplement is considered adulterated if it contains an undeclared pharmaceutical ingredient, a poisonous or deleterious substance, or is manufactured under conditions that do not meet cGMP. The FDA has particularly targeted supplements in categories like weight loss, sexual enhancement, and bodybuilding, where some manufacturers have been caught spiking products with undeclared drugs (sildenafil, sibutramine, anabolic steroids).

Even if you are not intentionally adulterating products, using untested raw materials from unreliable suppliers can result in contamination. Third-party testing of every batch is your best protection.

What Happens After a Warning Letter

You have 15 business days to respond in writing, explaining the corrective actions you have taken or will take. If your response is inadequate, or if you fail to respond, the FDA may escalate to product seizure, injunction (a court order to stop selling), consent decree, import alerts (if importing), or referral to the Department of Justice for criminal prosecution.

Even if the matter is resolved, the warning letter remains publicly searchable on FDA.gov indefinitely. Retailers, distributors, and savvy consumers will find it.

How to Protect Your Brand

1. Have every label reviewed by a regulatory consultant or experienced compliance team before printing
2. Audit your website, Amazon listings, and social media for disease claims quarterly
3. Vet your contract manufacturer's cGMP compliance before signing any agreement
4. Test every batch of finished product through a third-party lab
5. Maintain documentation of your claims substantiation
6. Monitor customer reviews and remove those making disease claims

CoreXponent Keeps You Compliant

CoreXponent builds compliance into every step of the brand development process — from formulation and manufacturing through Well Aliments to label design, claims review, and marketing copy. Our goal is to make sure your brand never appears on the FDA's warning letter page.