Due diligence looks different for a brand evaluating its first manufacturer than it does for an established brand considering a switch after years in production.
Established brands have very specific information to gather. They also have more at stake. A bad transition can strand supply, introduce quality problems into a mature product line, or create contractual complications that take months to unwind.
This checklist is written for brands that already understand supplement manufacturing basics and need a structured framework for evaluating a potential new manufacturing partner.
Section 1: Certifications and Quality Systems
Certifications are a valuable first-pass filter. A facility’s certification documentation tells you which third parties have audited its quality systems and how often.
Questions to Ask
- Which certifications does the facility currently hold, and can you provide copies of the certificates?
- Are your quality systems compliant with 21 CFR Part 111?
- Are you third-party cGMP certified?
- Are you NSF/ANSI 455-2 cGMP certified? Verify the certification through the NSF certification database.
- Have you received any FDA Warning Letters within the last three years? If so, are you willing to share them?
If they pertain to your product line, you may also ask:
- Do you hold NSF Certified for Sport® certification?
- Are you certified as a USDA Organic Handler?
What You’re Looking For
Third-party certifications from organizations such as NSF carry independent audit schedules with real consequences for nonconformance. Organic certification likewise provides independent verification for the applicable handling and production requirements.
Self-attested GMP is a manufacturer’s own statement that it follows GMP standards; no independent auditor has verified the claim. For brands selling through specialty retail or professional channels, the distinction matters, and retailers increasingly ask about it.
If a manufacturer claims NSF cGMP certification but will not provide its registration details for independent verification, treat that as a problem.
Section 2: Scope and Technical Capability
The better you understand your scope, the more quickly you can determine whether a manufacturer is a viable fit. It is common at this stage to ensure a signed nondisclosure agreement is in place so you can speak freely about your project.
Questions to Ask
- After reviewing our formula and packaging requirements, can you confirm that both are compatible with your services and equipment?
- How are label review and approval handled?
- Can you accommodate our specific testing requirements?
- If the facility is not third-party certified, how do you manage and reduce cross-contamination risk?
Important: Cross-contamination risk is especially important for products targeting tested athletes or brands with clean-label positioning. A facility that produces hormonal compounds or high-potency active ingredients on shared equipment may carry additional risk, even when cleaning validations are in place.
What You’re Looking For
Look for confident, direct, and easy-to-understand answers to your questions.
Remember that you may initially be speaking with a sales representative who does not have every answer. If necessary, request a meeting with company leadership or the quality team. Do not hesitate to involve technical stakeholders when you need more information to make the right choice for your brand.
Section 3: MOQs, Lead Times, and Scheduling
Questions to Ask
- What are your minimum order quantities for toll filling, custom manufacturing, and white-label programs?
- What does your current production lead time look like from documentation acceptance through product release?
- What is the typical turnaround time for a first run compared with recurring production runs?
- How is production scheduling managed?
- What happens to my production slot if there is a raw material delay on my end?
- Do you offer favorable scheduling or pricing arrangements for recurring purchase orders supported by predictable forecasting?
- What was your on-time release percentage over the last 12 months?
What You’re Looking For
On-time release percentage is a metric most facilities track. If a manufacturer does not have it readily available or provides a vague answer, that tells you something about how seriously it measures operational performance.
Lead-time answers should include the assumptions being made. A four-week lead time means something very different if it assumes all materials arrive on day one without issues than if it is measured from the date your purchase order is placed.
Section 4: Documentation and the Quality Agreement
Documentation is where the relationship either holds up under audit pressure or falls apart.
Questions to Ask
- What does a standard batch-release packet include?
- How quickly are release documents available after the product ships?
- Do you issue a Quality Agreement? If so, do you use a standard template, or are you willing to negotiate its terms?
- What is your process for handling out-of-specification (OOS) results?
- Who investigates an OOS result, what is the investigation timeline, and how is the brand notified?
- What is your change-control process?
- How and when are formula changes, supplier changes, equipment changes, or process changes communicated to brands?
- Do you retain batch records, and for how long?
What You’re Looking For
Depending on your project scope and the level of control you require over quality processes, the Quality Agreement can be one of the most important documents in the relationship. It defines who is responsible for each part of the manufacturing and quality-control process.
At a minimum, a Quality Agreement should address:
- Batch-release responsibility, including who approves release and which specifications are used
- OOS investigation responsibility and timelines
- Raw material testing and approval
- Change-notification requirements for supplier, equipment, formula, or process changes
- Recall procedures and communication protocols
- Record-retention periods
A Quality Agreement is particularly important if you need greater control over your quality-control processes or if you are the manufacturer of record for the material being packaged.
If you have verified the manufacturer’s certifications and prefer to be more hands-off, consider scheduling a discovery call with its quality team or quality representative. Use that conversation to confirm how each of the responsibilities above is handled.
Section 5: Communication and Relationship Structure
Questions to Ask
- Who will manage my account day to day, and what is their background?
- Who is my escalation contact for urgent quality issues?
- What is your expected response time for questions about active production?
- How do you communicate when something unexpected happens, such as a delay, OOS result, or material shortage?
- Do you have dedicated production-scheduling contacts, or does all communication route through account management?
- What does your onboarding process look like for new brands?
What You’re Looking For
Account management quality is difficult to assess before working with a manufacturer, but some behaviors during the sales process can serve as early indicators:
- Does the manufacturer acknowledge limitations and constraints, or does every response suggest that everything is possible?
- Does the team ask specific questions about your program, or does it appear to be following a generic sales script?
Manufacturers that are direct about constraints during the sales process are more likely to communicate clearly when something goes wrong during production.
The Facility Audit
For established brands committing significant annual volume, conducting a facility audit before signing is worth the time and cost.
What a Basic Audit Visit Should Include
- A tour of the production facility and warehousing areas
- A conversation with quality assurance or technical staff—not only the sales team
- A review of certifications, calibration logs, and relevant equipment-maintenance records
If a facility declines to allow an audit visit or restricts access to production areas without proper justification, factor that into your assessment.
Documents to Request Before Signing
Before committing to a new manufacturer, consider requesting:
- Current certification letters, including NSF, Organic, or other applicable certifications
- A sample Quality Agreement or Quality Agreement template
- A reference from a brand that has been in production with the manufacturer for at least 12 months
The reference conversation is often the most useful. Ask specifically: How has the manufacturer handled situations in which something went wrong?
Red Flags Summary
The following patterns are consistent signals that a manufacturer relationship may create problems:
- Certifications that cannot be verified through public databases
- Resistance to establishing a Quality Agreement when one is appropriate
- Frequent account-management changes without a structured handoff
- Verbal commitments without follow-through
- Vague answers to technical questions that do not improve with follow-up
- No clear escalation path for quality issues
None of these issues is necessarily disqualifying on its own. A pattern of them across a single evaluation should be treated seriously.
One Final Note
The best due diligence conversation you can have with a prospective manufacturer may also be the one that reveals the most. Describe a production problem you have experienced in the past—a late release, an OOS result, or a material shortage—and ask how the manufacturer would have handled it.
How a manufacturer thinks about problems it has not encountered with you yet can tell you more about what the relationship will look like than any reference check.