Underdosing and overage patterns in test data

When independent laboratories test peptide products sold for research use, the quantity on the label and the quantity in the vial rarely match exactly. That gap, positive or negative, is one of the more practically useful numbers test aggregators collect. Knowing what it usually means helps researchers read certificates of analysis (COAs) and batch reports more critically.

What "labeled vs. tested" quantity data shows

Contract analytical labs such as Janoshik Analytical, an independent testing lab based in Prague that is widely used in the research-peptide community, run HPLC-based mass and purity assays and confirm identity by mass spectrometry. Aggregator platforms such as Finnrick, Peptigrity, VialAudit, and PeptideBenchmark then collect independent test results across many vendors and lots. Some of these platforms commission their own testing. Finnrick, for example, states in its published methodology that it crowdsources samples and sends them to third-party labs for HPLC analysis, scoring both purity and quantity accuracy (the actual amount present versus the vendor's claim). When a product label reads "5 mg" and a mass assay returns 5.4 mg, that 8% surplus is logged as a positive overage. When the assay returns 4.3 mg, the 14% shortfall is a negative overage, commonly called underdosing.

Across publicly available test datasets, results fall into three rough patterns: products that land within a narrow band of label claim (roughly ±5–10%), products that run meaningfully above label claim, and products that fall meaningfully below it. The distribution is lopsided. The research community has noted that underdosing shows up less often in products from suppliers who submit to routine third-party testing, though gaps still occur.

Overage as a manufacturing buffer

A modest positive result above label claim is common in research-chemical and supplement manufacturing. A small overage may be present to offset degradation over shelf life, minor losses during lyophilization or fill-and-finish, and the inherent variance of analytical methods. In the regulated pharmaceutical world, though, overage is not a free-pass "standard practice." Under USP and ICH guidance, using an overage of a drug substance to compensate for degradation during manufacture or over shelf life is generally discouraged and must be justified on safety and efficacy grounds. The older USP overage factor used for stability losses has since been removed from the current text. Established peptide CDMOs that serve regulated markets, firms such as Bachem and PolyPeptide Group, operate under those tighter specification and stability frameworks rather than open-ended overage windows.

For research-grade peptides, then, a product testing modestly above label claim is not automatically a concern. It may reflect intentional buffer, lot-to-lot variability, or both. The more useful signal is whether the deviation is consistent across lots from the same source, which points to controlled manufacturing, or erratic, which can point to inconsistent process control.

Underdosing as a red flag

A small overage carries a plausible benign explanation. Underdosing, receiving meaningfully less material than the label claims, has a narrower set of explanations, most of them unfavorable. Possible causes include inaccurate filling by the manufacturer, deliberate short-filling to cut cost, degraded material that has lost mass over time (often correlated with failed purity results), or simple mislabeling. Aggregated test data published by platforms such as VialAudit and PeptideBenchmark shows that low quantity results frequently co-occur with purity problems, which suggests a shared root cause in manufacturing or storage rather than an isolated weighing error.

Regulators have flagged label-accuracy problems in the broader gray market. In late 2024 the FDA issued a wave of warning letters to companies selling peptides online for human use despite "research use only" labeling. On September 30, 2025 it published Import Alert 66-78, authorizing detention without physical examination of certain drugs based on analytic test results and adding further unapproved peptides to its enforcement list. These actions are a reminder that research-only material is not approved for human consumption, and that independent quantity and purity data is worth scrutinizing.

Testing platforms and community documentation advise researchers reviewing supplier test records to treat a single underdosed result with caution, and a pattern of underdosed results across multiple lots as a meaningful quality signal. Vendor-supplied COAs are useful, but they do not substitute for independent third-party testing, because the testing lab is not beholden to the seller.

Reading test data in context

No single data point tells a complete story. A mass assay result should be read alongside purity (HPLC area %), identity confirmation (typically mass spectrometry), and lot consistency over time. Overage and underdosing figures published by independent aggregators are a snapshot of what was tested at a specific time from a specific lot. They do not guarantee future lots will perform identically. Researchers sourcing peptides for laboratory study should treat third-party quantity data as one input in a broader quality evaluation, not a pass/fail verdict on a supplier.

Sources

• Finnrick — testing and rating methodology
• Janoshik Analytical — HPLC and MS testing services
• Peptigrity — independent peptide quality data
• VialAudit — independent peptide vendor audits
• PeptideBenchmark — independent vendor reviews and data
• USP — 100% Label Claim and Overages (stakeholder briefing)
• FDA — Import Alert 66-78 (detention without physical examination, analytic test results)