FDA Warning Authority: How the Agency Enforces Compliance Against Non-Compliant Manufacturers

The U.S. Food and Drug Administration doesn’t just approve drugs and inspect factories-it enforces the rules. When manufacturers cut corners, mislabel products, or skip safety steps, the FDA doesn’t wait. It acts. And one of its most powerful tools is the FDA warning letter.

These aren’t gentle reminders. They’re formal notices that say: You’re violating federal law. Fix it now-or face serious consequences. Since the 1970s, warning letters have been the FDA’s go-to first step in holding companies accountable. But in recent years, the tone, frequency, and stakes have changed dramatically.

What Exactly Is an FDA Warning Letter?

An FDA warning letter is a written notice sent to a company after an inspection or complaint reveals violations of the Federal Food, Drug, and Cosmetic Act (FDCA). It’s not a fine. It’s not a shutdown. But it’s the official signal that the FDA is watching-and ready to escalate.

Warning letters list specific problems: contaminated ingredients, false claims on labels, missing quality controls, unapproved drug manufacturing, or even deceptive marketing on social media. Each violation is tied to a federal regulation. For example, a pharmaceutical company might be cited under Section 502(a) for misbranding, or Section 502(bb) for selling compounded drugs with unapproved claims.

Companies get just 15 business days to respond. That’s not a suggestion. It’s a deadline. The response must detail exactly how they’ll fix each issue, when it’ll be done, and how they’ll prevent it from happening again. If the FDA isn’t satisfied, the next step isn’t another letter-it’s legal action.

The Shift in Enforcement: From Lenient to Aggressive

For years, the FDA was seen as slow-moving and reluctant to crack down hard. That changed in early 2023. Commissioner Robert Califf and Deputy Commissioner Norman Sharpless announced a return to the enforcement style of the 1990s: hundreds of warning letters a year, not dozens.

The numbers back it up. In 2024 alone, the FDA issued 149 warning letters to human food manufacturers for failing to follow Current Good Manufacturing Practices (cGMP). Another 37 went to animal food companies. In the first half of 2025, 58 warning letters targeted compounding pharmacies and telehealth firms selling unapproved versions of GLP-1 drugs like semaglutide and tirzepatide.

What’s new? The letters themselves. They’re now signed by the directors of the Center for Drug Evaluation and Research (CDER) or the Center for Biologics Evaluation and Research (CBER)-not junior reviewers. That signals top-level accountability. The language has hardened too. Older letters said, “We request you stop.” New ones say, “FDA requests you take immediate action.” There’s no ambiguity.

How the FDA Targets Different Industries

The FDA doesn’t treat all industries the same. Enforcement priorities vary by product type-and the consequences do too.

Tobacco products are under intense scrutiny. Since 2021, the FDA has issued over 700 warning letters to companies selling unauthorized electronic nicotine delivery systems (ENDS), especially those marketed to teens. These letters often cite failure to submit a premarket tobacco application (PMTA), which is required by law. Even if the product is popular, if it’s not approved, it’s illegal.

Pharmaceuticals face scrutiny over compounding pharmacies that act like drug manufacturers. These companies mix drugs like semaglutide and claim they’re “customized” to avoid FDA approval. The FDA calls it misbranding. Warning letters now explicitly state these products are not safe or effective, and the agency is cracking down hard.

Food manufacturers are being held to new standards under the Food Safety Modernization Act (FSMA). Instead of just citing outdated cGMP rules, the FDA now cites Preventive Controls for Human Food. This means companies must prove they’ve identified risks-like allergen cross-contact or pathogen contamination-and have systems in place to stop them before they happen.

Imported products are stopped at the border. If an inspection finds issues, the FDA issues an Import Alert. That means the product gets detained without physical examination (DWPE). The importer has 30 days to prove the shipment is safe. If they can’t, the goods are refused entry-and often destroyed.

Grocery store owner reads an FDA warning letter about unapproved supplements while customers shop nearby.

What Happens If You Ignore the Letter?

Ignoring a warning letter is a recipe for disaster. The FDA doesn’t wait. If a company doesn’t respond-or responds poorly-the agency has a full toolbox of escalating penalties:

Civil Monetary Penalties (CMPs): Up to $1 million per violation under 21 U.S.C. § 333(f). For a company with multiple violations, that can mean millions.
Product seizures: The FDA can seize unsafe or misbranded products in warehouses or at ports.
Injunctions: A federal court can order a company to stop manufacturing or selling a product.
Withdrawal of approval: For drugs, the FDA can revoke marketing authorization. That means the product disappears from shelves permanently.
Criminal charges: Under Section 303(f) of the FDCA, companies that delay, deny, or limit inspections can face criminal prosecution. This includes redacting documents, refusing access to facilities, or providing incomplete records.

Foreign manufacturers aren’t safe either. In May 2025, the FDA expanded its unannounced inspection program for overseas facilities. The goal? Increase inspections by 300% over the next two years. If a foreign plant fails an unannounced inspection, it gets a Form 483-and if the issues aren’t fixed, a warning letter follows. No warning. No notice. Just inspectors showing up.

Real-World Consequences: When Compliance Fails

In 2024, a compounding pharmacy in Florida received a warning letter for selling compounded semaglutide with claims that it was “FDA-approved” and “as effective as Ozempic.” The company didn’t respond. Three months later, the FDA seized $2.3 million in inventory. Two executives were charged with misbranding. The company shut down.

Another case involved a U.S.-based supplement maker that used social media influencers to promote weight-loss claims without scientific backing. The FDA issued a warning letter. The company posted a vague apology but kept selling. Within six weeks, the FDA filed for an injunction. The website was taken offline. The brand’s Amazon listings were removed.

These aren’t rare. They’re becoming the norm.

FDA inspectors arrive at a foreign-made supplement factory at dawn, confronting workers with import alerts.

How Companies Should Respond

If you get a warning letter, treat it like a medical emergency. Here’s what works:

Don’t delay. The 15-day clock starts the moment the letter is delivered. Every day counts.
Don’t guess. Hire an FDA compliance lawyer. Don’t rely on in-house staff who’ve never handled a warning letter before.
Don’t overpromise. Your response must be specific, factual, and backed by evidence. Saying “we’ll improve” won’t cut it. You need timelines,责任人, and documentation.
Don’t ignore the root cause. Fixing one problem isn’t enough. You need to fix your entire quality system. Otherwise, the same issue will pop up again.
Don’t underestimate follow-up. The FDA will send inspectors back. They’ll check your records, interview staff, and verify your fixes. Be ready.

Companies that respond quickly and thoroughly often avoid further action. Those that drag their feet? They end up in court.

What’s Next for FDA Enforcement?

The FDA’s 2026 budget request includes $50 million to boost inspection capabilities and enforcement staff. More inspectors. More unannounced visits. More digital monitoring of websites and social media. The agency is building a system that doesn’t wait for complaints-it hunts for violations.

Expect more warning letters targeting digital marketing. More focus on foreign supply chains. More penalties for companies that try to hide behind vague claims like “natural” or “herbal.” The era of regulatory leniency is over.

If you’re a manufacturer, distributor, or marketer of FDA-regulated products, compliance isn’t optional. It’s survival.

What happens if I don’t respond to an FDA warning letter?

If you don’t respond within the deadline-or if your response is inadequate-the FDA can escalate to civil penalties, product seizures, injunctions, or even criminal charges. The agency doesn’t wait. It moves quickly to protect public health, and ignoring a warning letter is seen as intentional noncompliance.

Are FDA warning letters public?

Yes. All FDA warning letters are posted publicly on the agency’s website. They’re searchable by company name, product type, or date. This transparency is intentional-it serves as a warning to other companies and informs the public about safety risks.

Can a company appeal an FDA warning letter?

You can’t formally appeal a warning letter, but you can request a meeting with the FDA to discuss the findings. Some companies use this to clarify misunderstandings or provide additional evidence. However, if the violations are clear and documented, the letter stands. The real focus should be on fixing the problem, not arguing the letter.

What’s the difference between a warning letter and an Untitled Letter?

An Untitled Letter is for minor or technical violations-like a small labeling error or an unclear claim. It’s less formal and doesn’t require a formal response. A Warning Letter is for serious, regulatory-significance violations that threaten public health. It demands a detailed corrective plan and triggers serious consequences if ignored.

Do FDA warning letters apply to foreign companies?

Yes. Foreign manufacturers are subject to the same rules. If your facility is inspected and found in violation, you’ll receive a warning letter-even if you’re based in China, India, or Germany. And if you don’t respond, your products will be detained at U.S. ports under an Import Alert. Many foreign companies have lost access to the U.S. market because they ignored these letters.

How long does it take the FDA to follow up after a warning letter response?

The FDA typically conducts a follow-up inspection within 3 to 6 months. For high-risk industries like pharmaceuticals or compounding pharmacies, inspections may come sooner. The agency checks whether your corrective actions were actually implemented and whether they’re effective. If not, enforcement escalates immediately.

Can a warning letter affect a company’s ability to get FDA approval for new products?

Absolutely. The FDA reviews a company’s compliance history when evaluating new applications. A recent warning letter can delay approval for months-or lead to outright rejection. Companies with a pattern of violations are often placed on a “watch list,” which triggers more scrutiny and longer review times.