Quality Control and Testing of Dietary Supplements: Private Labeler Responsibilities

Private labelers in the dietary supplement industry rely heavily on contract manufacturers to produce their branded products. While this arrangement allows for flexibility and scalability, private labelers must take proactive steps to ensure that quality control and regulatory compliance are maintained. The FDA holds private labelers accountable for the safety, accuracy, and labeling of their products, even when manufacturing is outsourced.

Understanding Private Labeler Obligations

Although contract manufacturers handle production, testing, and ingredient sourcing, private labelers cannot rely solely on them for regulatory compliance. Under Current Good Manufacturing Practices (cGMPs) for Dietary Supplements (21 CFR Part 111), private labelers are responsible for:

• Ensuring the contract manufacturer complies with cGMP regulations for testing, processing, and handling dietary supplements.

• Verifying product claims, labeling accuracy, and ingredient integrity to prevent misbranding.

• Conducting independent testing or audits to confirm purity, potency, and safety.

• Maintaining documentation and supplier agreements to prove compliance in case of FDA inspection.

• Responding to adverse event reports and product recalls—private labelers must act swiftly in cases of contamination or mislabeling.

Key Testing Requirements for Private Label Supplements

Since private labelers market the final product, they should require or conduct additional testing beyond what their contract manufacturer provides. Common testing areas include:

1. Microbial Testing – Verifies the absence of pathogens such as Salmonella, E. coli, and mold.

2. Heavy Metal Screening – Ensures compliance with FDA and Proposition 65 limits for lead, arsenic, cadmium, and mercury.

3. Identity and Potency Verification – Confirms ingredient authenticity using high-performance liquid chromatography (HPLC) or DNA barcoding.

4. Shelf-Life and Stability Testing – Ensures label claims remain valid throughout the product’s lifecycle.

5. Disintegration and Absorption Testing – Verifies that capsules or tablets dissolve properly for bioavailability.

Selecting a Compliant Contract Manufacturer

Private labelers should conduct thorough due diligence before partnering with a contract manufacturer. Key considerations include:

• Does the facility maintain cGMP certification?

• Is it NSF, USP, or ISO 17025 accredited for third-party testing?

• Are batch records and Certificates of Analysis (COAs) provided for each production run?

• Do they perform independent verification for contaminants and potency?

A strong supplier qualification program ensures private labelers mitigate risks and uphold product integrity.

Mitigating Legal and Regulatory Risks

Failure to ensure proper quality control and testing can lead to FDA warning letters, product recalls, or lawsuits. To minimize risk:

• Private labelers should require signed supplier agreements outlining compliance expectations.

• Regular audits and independent testing should be part of routine quality assurance measures.

• Clear labeling and advertising claims must align with FDA and FTC regulations to avoid misbranding violations.

• Consumer complaint tracking is essential for identifying potential safety concerns early.

Final Thoughts

Private labelers must take an active role in quality control even when using contract manufacturers. Implementing a robust testing and compliance strategy ensures product safety, regulatory compliance, and brand integrity—ultimately building trust with consumers.