CGMP Systems That Prevent FDA Warning Letters for Dietary Supplements

A recent FDA enforcement action against a dietary supplement manufacturer is a useful reminder that CGMP compliance in this space is not optional — and the consequences of getting it wrong are public, costly, and hard to recover from. This article uses that enforcement pattern as a case study in what goes wrong and, more importantly, what prevents it.

What the FDA Actually Looks for When It Inspects a Supplement Facility

When FDA investigators walk into a dietary supplement facility, they are working through 21 CFR Part 111 — Current Good Manufacturing Practice in Manufacturing, Packaging, Labeling, or Holding Operations for Dietary Supplements. That regulation is the governing framework, and it covers everything from personnel qualifications to laboratory controls to labeling accuracy.

The March 2026 warning letter issued to Nupack Inc. (FDA Warning Letter 722113, dated March 20, 2026) cited violations under 21 CFR Part 111, and alleged that products were adulterated and misbranded under the Federal Food, Drug, and Cosmetic Act. Specifically, the letter referenced products making claims related to blood glucose regulation and diabetes support — the kind of language that simultaneously raises structure/function claim concerns and invites scrutiny of whether the product has crossed into drug territory.

That combination — CGMP violations plus labeling and claims issues — is one of the more serious enforcement profiles FDA can bring. And it is almost entirely preventable with the right systems in place.

The Two Compliance Failures That Show Up Together Most Often

In my experience working with dietary supplement manufacturers, CGMP failures and labeling violations rarely show up in isolation. They tend to cluster, and for a straightforward reason: the same quality culture that allows a manufacturing deviation to go unaddressed is usually the same culture that lets a product claim slide through without a substantiation review.

FDA enforcement data supports this pattern. According to FDA's warning letter database, dietary supplements consistently rank among the top product categories cited for CGMP violations, and a significant portion of those letters include both manufacturing and labeling allegations in the same action.

Think about what that means practically. If your organization treats CGMP as a paperwork burden and your label review process as a marketing function, you are building toward both problems at the same time.

Here is how to pull them apart and address each one.

CGMP Compliance Under 21 CFR Part 111: Where the Gaps Actually Are

21 CFR Part 111 has been in effect since 2008 — phased in based on company size, with full compliance required for all manufacturers by June 2010. There is no grace period anymore. When FDA finds a violation today, they are not finding a new company learning the rules. They are finding a company that has had more than 15 years to build compliant systems.

The most common gap areas I see across the dietary supplement clients I work with fall into a few categories:

Master Manufacturing Records (MMRs) and Batch Records

21 CFR 111.205 requires a written Master Manufacturing Record for each unique formulation and batch size. 21 CFR 111.255 requires batch production records that document, for every batch, the actual execution of each step in the MMR. The failure mode here is usually one of two things: the MMR exists but is incomplete (missing specifications for yield, for example), or the batch records are being completed after the fact rather than in real time.

Neither of those is a paperwork technicality. They are the difference between a record system that can detect a deviation and one that cannot.

Laboratory Controls and Finished Product Testing

21 CFR 111.75 requires testing of components, in-process materials, and finished batches to verify identity, purity, strength, and composition. The regulation does not allow a company to rely entirely on a certificate of analysis from a supplier without establishing the reliability of that supplier's testing through its own confirmatory analysis — at minimum, identity testing on every ingredient lot.

This is an area where smaller manufacturers frequently cut corners, and it is an area FDA specifically looks for. If you are not testing incoming ingredients for identity, you do not know what is in your product. It is that direct.

Qualified Personnel and Training Records

21 CFR 111.12 requires that personnel who manufacture, package, label, or hold dietary supplements be qualified by education, training, or experience to perform their assigned functions. The regulation also requires written procedures and documented training.

What I find in practice is that training programs exist on paper but are not verified for effectiveness. Someone signed a form. That is not training.

Equipment Qualification and Cleaning Validation

21 CFR 111.27 covers equipment design, construction, and maintenance. Cross-contamination through inadequate cleaning procedures is a real manufacturing risk, and it is one that FDA can identify through documentation review alone, without needing a sample to test. If your cleaning procedures are not validated and your equipment logs are incomplete, that is a finding waiting to happen.

The Labeling Problem: When Claims Create a Drug Definition

This is the piece of the Nupack enforcement action that I think deserves the most attention from supplement manufacturers, because it is genuinely easy to walk into without realizing it.

Under 21 U.S.C. 321(g)(1), a product intended to treat, mitigate, cure, or prevent a disease is a drug — regardless of what it is called on the label. If a dietary supplement makes a disease claim (as opposed to a structure/function claim), FDA can regulate it as an unapproved new drug. That changes the entire compliance framework overnight.

The products cited in the Nupack warning letter included language like "natural diabetic supplement powder mix for daily diabetes support" and references to regulation of blood glucose levels. Under FDA's reading of the statute, language that implies management of a disease condition (diabetes) rather than support of a normal body function (healthy glucose metabolism) is a disease claim — and a disease claim on a supplement label creates a serious regulatory problem.

The practical distinction matters:

The line between these categories is not always obvious, and FDA has issued guidance on structure/function claims (published January 2000, updated guidance available through FDA's CFSAN). In my view, any company selling a product in the metabolic health, blood sugar, or diabetes-adjacent space needs a qualified regulatory review of every claim before the label goes to print — not after.

According to FDA's Dietary Supplement Ingredient Advisory List and enforcement history, products making claims related to glucose regulation and diabetes management receive elevated scrutiny, and that scrutiny is unlikely to decrease given current enforcement priorities.

What a Prevention-Focused Quality System Actually Looks Like

The companies that avoid warning letters are not necessarily doing something dramatically different from everyone else. They have built a few core systems and they actually use them.

A Document Control System You Can Defend in an Inspection

Every procedure needs a version number, an effective date, an owner, and a review cycle. That is the minimum. But more importantly, procedures need to reflect what people actually do — not what someone thought they would do in 2012 when the SOP was first written. The gap between written procedure and actual practice is something FDA investigators are trained to look for, and they find it by comparing your SOPs to your records.

A CAPA Program That Closes Loops

Corrective and preventive action (CAPA) is not required by name in 21 CFR Part 111, but it is implied throughout — particularly in 21 CFR 111.103, which requires written procedures for quality control operations. A functioning CAPA program captures deviations, identifies root causes, and documents that the corrective action actually worked. The companies that get into trouble are the ones with a CAPA log full of open items and no evidence that anything changed.

A Label Review Process With Regulatory Sign-Off

Marketing should not be the last word on label claims. I am not saying marketing does not have a role — of course they do. But there needs to be a regulatory review step, with someone who knows FDA's claims guidance, before the label is finalized. Structure/function claims also require a notification to FDA within 30 days of first marketing (under 21 CFR 101.93), and they require a disclaimer on the label. Both of those requirements are routinely missed.

Supplier Qualification That Goes Beyond a Questionnaire

21 CFR Part 111 requires that you qualify your ingredient suppliers. A questionnaire is a starting point, not an ending point. You need to understand your suppliers' testing capabilities, review their CoAs against your own confirmatory testing, and have a written approval process that documents the basis for qualification. When FDA finds an adulteration issue, they will trace it back to your supplier qualification program — and if that program is weak, you own the problem even if the supplier caused it.

The Specific Regulations You Need to Know

For any dietary supplement manufacturer reading this, here is the core regulatory map:

• 21 CFR Part 111 — Current Good Manufacturing Practice for dietary supplements (the primary CGMP framework)
• 21 CFR Part 101 — Food labeling, including structure/function claim requirements at 21 CFR 101.93
• 21 U.S.C. 321(g)(1) — The statutory definition of a drug, which determines when a supplement label creates a drug compliance problem
• 21 U.S.C. 331(a) — Prohibited acts, including introduction of adulterated or misbranded food into interstate commerce (the provision cited in the Nupack warning letter)
• DSHEA (Dietary Supplement Health and Education Act of 1994) — The foundational statute that established the current regulatory framework for dietary supplements

An FDA warning letter citing adulteration and misbranding under these provisions typically triggers a requirement to respond within 15 working days of receipt. The FDA Warning Letter to Nupack Inc. (722113) was issued March 20, 2026, which means the response window has already opened. More broadly, companies that receive warning letters without adequate CGMP systems in place to document remediation are at risk of escalating enforcement — including injunctions, seizures, and import alerts.

A Statistical Snapshot of Where the Industry Stands

It is worth grounding this conversation in some data, because I think the scale of the problem surprises people.

According to FDA's 2023 Summary of Warning Letters, dietary supplements and food products were among the most frequently cited categories for CGMP-related violations. The dietary supplement industry in the United States is estimated at over $56 billion annually (Council for Responsible Nutrition, 2023 estimates), yet FDA studies have found that a significant percentage of dietary supplement products tested do not contain the labeled amount of active ingredients — a direct CGMP failure.

FDA issued more than 300 warning letters in fiscal year 2023 across all product categories, with dietary supplements representing a consistent and substantial share of that enforcement activity year over year. For companies in this space, that is not a background statistic — that is a meaningful probability.

If You Are in the Metabolic Health or Blood Sugar Space, Read This Section Twice

I want to be direct about something. The regulatory risk for companies selling products that reference blood sugar, glucose metabolism, insulin function, or diabetes in any form is materially higher than for companies selling, say, a multivitamin. FDA has been consistent and increasingly aggressive in its enforcement against products in this category that make disease claims, and the analysis is not complicated: if your product name or your label copy implies it manages a disease condition, you have a labeling problem that no amount of CGMP compliance will fix.

The answer is not to avoid the category. It is to be precise about your claims, get them reviewed by someone who knows the regulatory framework, and make sure your label, your website, and your Amazon listing all say the same thing — because FDA looks at all of them.

One thing I tell clients: your label review process is not complete until someone has audited your third-party seller listings, your social media, and any influencer content you have authorized. All of that content can be attributed to your company's intended use of the product.

How Certify Consulting Approaches Dietary Supplement CGMP

At Certify Consulting, I have worked with dietary supplement manufacturers at every stage — from pre-launch companies building their first quality system to established brands preparing for FDA inspections. The work is practical and specific. We build the actual systems: the MMRs, the batch record templates, the supplier qualification programs, the label review processes.

Across more than 200 clients, we have maintained a 100% first-time audit pass rate. That is not because the audits were easy — it is because we build systems that work before the investigator arrives.

If your company is in the dietary supplement space and you are not confident your CGMP program would hold up to an unannounced FDA inspection, that is worth addressing now. The warning letter process is public record. The reputational and operational cost of that outcome is significant, and it is avoidable.

You can reach our team at certify.consulting to discuss where your program stands.

Related Resources

• Dietary Supplement CGMP Compliance Services
• FDA Inspection Readiness for Food and Supplement Facilities

Last updated: 2026-05-05

Source reference: FDA Warning Letter to Nupack Inc., 722113, issued March 20, 2026. Available at fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/nupack-inc-722113-03202026