5 Most Common Reasons for FDA Warning Letters (and How to Avoid Them)

If you browse the FDA’s Warning Letter database for just ten minutes, you’ll start to notice something: the same violations appear over and over.

It’s not that the FDA is fixated on a few pet rules — it’s that certain compliance failures are so common, and so high-risk, that they demand swift action every time.

Take the case of Green Valley Naturals, a small supplement brand that received a warning letter in 2024. The violations? Unapproved drug claims, missing manufacturing records, and untrained staff. Three of the most common — and preventable — mistakes in the industry.

This guide breaks down the top five reasons FDA warning letters are issued, why they matter, and how to keep them out of your business.

GMP & Manufacturing Violations

What it is:

CGMP — Current Good Manufacturing Practice — regulations (21 CFR Parts 210 & 211 for drugs, 21 CFR Part 111 for supplements) require strict controls over how products are made, tested, and stored.

Why it matters:

Poor manufacturing practices can lead to contamination, incorrect dosages, or unsafe products — directly threatening public health.

Example:

In 2023, a sterile injectables manufacturer was cited for failing to maintain cleanroom sterility and allowing unqualified staff to handle aseptic operations.

How to avoid it:

• Conduct regular internal GMP audits.
• Maintain validated cleaning procedures.
• Train and re-train all production staff annually.

Misbranding & Mislabeling

What it is:

Misbranding occurs when a product label contains false or misleading information, omits required details, or makes unauthorized claims.

Why it matters:

Consumers rely on accurate labels to make safe choices. The FDA views misleading labeling as a direct risk to public health.

Example:

A beverage company was cited for claiming its drink could “cure arthritis” — instantly classifying it as an unapproved drug.

How to avoid it:

• Have regulatory review every label and marketing material.
• Never make therapeutic claims without FDA approval.
• Keep labeling SOPs updated and enforced.

Failure to Report Adverse Events

What it is:

Manufacturers, packers, and distributors must report serious adverse events (like hospitalizations or deaths) to the FDA within specific timeframes.

Why it matters:

Delayed reporting can lead to preventable harm and signals to the FDA that you’re not prioritizing consumer safety.

Example:

A cosmetic brand was cited for failing to report multiple consumer hospitalizations linked to allergic reactions from its product.

How to avoid it:

• Train customer service to flag all health complaints.
• Maintain an adverse event reporting SOP.
• File reports electronically as soon as possible.

Import & Export Violations

What it is:

Imported products must meet all U.S. standards before entry. Violations include undeclared ingredients, non-compliant labeling, and manufacturing outside GMP standards.

Why it matters:

The FDA partners with Customs and Border Protection (CBP), and flagged shipments can be refused entry or destroyed.

Example:

A foreign-made dietary supplement was detained at port for containing undeclared prescription drugs.

How to avoid it:

• Audit overseas suppliers regularly.
• Use pre-shipment compliance testing.
• Keep records of supplier GMP certifications.

Clinical Trial Noncompliance

What it is:

Violations in clinical research — enrolling ineligible subjects, missing informed consent, failing to maintain accurate study records.

Why it matters:

Data integrity and participant safety are at the heart of FDA oversight in trials.

Example:

A device manufacturer failed to collect signed consent forms for half of its study participants, invalidating its trial data.

How to avoid it:

• Have IRB oversight on all trials.
• Use centralized record-keeping systems.
• Train research staff on GCP (Good Clinical Practice) standards.

Conclusion

While the specific details of FDA warning letters may vary, the core message is consistent: compliance isn’t a once-a-year event — it’s a daily habit.

The companies that avoid these top five violations aren’t lucky. They build systems, train their people, and monitor themselves with the same scrutiny the FDA would.

And remember: every one of these violations has been prevented countless times by companies that made compliance part of their culture. Yours can too.