FDA Issues Numerous Warning Letters

March 12, 2024

The U.S. Food and Drug Administration (FDA) uses warning letters to notify manufacturers that they have violated the FDA’s regulations or federal law. Manufacturers that receive warning letters must respond promptly, and they must take appropriate measures to come into compliance. After issuing a warning letter, FDA checks to ensure that the company’s corrections are adequate. Ignoring a warning letter, or providing an incomplete response, puts a company at significant risk of enforcement action by the Agency.

In the past year, FDA issued a significant number of warning letters as the Agency continues to prioritize enforcement. Companies that receive warning letters must respond appropriately to avoid consequences such as expensive litigation and unnecessary damage to their reputation.

Notable FDA Warning Letters: December 2023

The FDA’s warning letters posted in December 2023 include the following noteworthy examples:

  • The FDA sent a warning letter to a foreign medical device manufacturer alleging that its devices were adulterated, “in that the methods used in, or the facilities or controls used for, their manufacture, packing, storage, or installation are not in conformity with the current good manufacturing practice requirements.” The FDA’s letter also notes that the company’s prior responses to the Agency's  concerns were inadequate to come into compliance with the Food, Drug and Cosmetic Act (FDCA) and applicable regulations. In light of the alleged persistent failures, the letter requests that the manufacturer respond with an explanation of “the specific steps your firm has taken to address the noted violations, including an explanation of how your firm plans to prevent these violations, or similar violations, from occurring again.”
  • The FDA sent a warning letter to a domestic drug manufacturer after observing both a “mold-like substance on an air conditioning unit sleeve,” and “insects both alive and dead, and other animal waste,” in a bulk storage facility during an inspection. The letter also states that the manufacturer failed to properly respond to the FDA’s inspection report because it failed to include “a review of environmental monitoring data . . ., an adequate risk analysis of previously manufactured drug product, or testing of reserve samples from impacted batches.”
  • The FDA sent a warning letter to a domestic cosmetic and body care product company alleging multiple violations of the FDCA. The alleged violations included failure to establish standard operating procedures to ensure appropriate standards of quality and purity, failure to properly maintain and sterilize equipment, failure to maintain cleaning records, failure to have an “adequate and efficient quality unit,” and failure to maintain adequate stability data, among others.

FDA Warning Letters: What Manufacturers Need to Know

1. Several FDA Offices Issue Warning Letters

Several FDA Offices issue warning letters. These include the Center for Devices and Radiological Health (CDRH), the Center for Drug Evaluation Research (CDER), the Center for Biologics Evaluation and Research (CBER), among others. Each of these offices has its own enforcement priorities, and identifying the specific office that issued a warning letter (and why) is one of the first steps toward formulating an informed response.

2. Warning Letters Can Address Several Violations

Warning letters can also address several different types of violations. This is illustrated by the example warning letters from December 2023 summarized above. Additionally, warning letters issued so far in 2024 have identified violations including (but not limited to):

  • Noncompliance with Current Good Manufacturing Practice (CGMP) guidelines

  • Inadequate hazard analysis and risk-based preventive controls

  • Compounding pharmacy noncompliance

  • Adulterated drug products and finished pharmaceuticals

  • Unapproved and misbranded new drugs

  • Investigational Device Exemption (IDE) and Premarket Approval Application (PMA) noncompliance

  • Failure to register and list produces in compliance with the Food, Drug and Cosmetic Act

This is just a small sampling. As the FDA’s recent warning letters make clear, all forms of noncompliance present risks for enforcement in 2024.

3. Receiving a Warning Letter Can Present Substantial Risks

FDA issues these letters when “a manufacturer has significantly violated FDA regulations.” If a company fails to effectively address the allegations in a warning letter, this can lead to prompt and aggressive enforcement action.

4. Companies that Receive Warning Letters Must Carefully Assess Their Compliance Programs

In light of these risks, companies that receive warning letters from the FDA must carefully assess their compliance with applicable laws and regulations. They must work quickly to determine what changes (if any) need to be made, and they must determine what remedial actions (if any) are warranted. They must also ensure that their policies, procedures, and work instructions are adequate to prevent repeat violations. Facing repeated scrutiny from the FDA and other law enforcement authorities can increase the risk of incurring substantial penalties and harming a company’s reputation.


Manufacturers that receive FDA warning letters need to respond promptly and thoughtfully to avoid enforcement action. If you need help responding to an FDA warning letter, please contact us.