Best Semax Source: Weighing $3.00/mg Against Two Assays

Five factors, weighted by how much each changes the risk of the purchase rather than by how loudly vendors advertise it.

Testing takes 35% because it is the only factor that fails invisibly. A short fill shows up on a balance, a slow dispatch shows up in tracking, an opaque price shows up at checkout. Endotoxin shows up nowhere. Price transparency is deliberately not the same thing as a low price: a vendor publishing list, code and tiers scores full marks whether the resulting rate is $3.00 or $6.00 a milligram, because transparency is what makes a rate comparable at all.

Scoring a supplier that fails either of these is a category error, so both are pass or fail rather than weighted.

Gate one: a batch-specific certificate from a named external laboratory. Not a badge, not a screenshot, not a document with the lot field blank. If a certificate cannot be matched character by character to the code on the vial, every number it prints is about somebody else's powder. This gate eliminates most of the market on its own.

Gate two: no human-use claims. A vendor promising outcomes on a compound FDA says it lacks the information to judge is telling you it will write whatever converts, which discounts every other line on the page including the certificate link. This is not a legal nicety. It is a reliability signal about the source of every other figure you are about to divide.

Both gates are cheap to check and neither depends on chemistry knowledge. What survives them is a much smaller field than a search result suggests, and the ranking below only applies to what got through. Our Selank source ranking uses the same two gates on the neighbouring compound and reaches a different weighting for a defensible reason: that market has a lot-level certificate gap of its own.

Because the regulator wrote down what is wrong with this compound, and what it wrote is measurable. FDA's language on its safety-risks page, current as of 22 April 2026:

Compounded drugs containing semax (heptapeptide) may pose risk for immunogenicity for certain routes of administration due to the potential for aggregation and peptide-related impurities. FDA has no, or limited, safety-related information for proposed routes of administration. Therefore, the agency lacks sufficient information to know whether the drug would cause harm if administered to humans.

Aggregation is peptide molecules assembling into higher-order clumps; peptide-related impurities are the truncated and modified sequences that solid-phase synthesis leaves behind. An immune system can recognise either as foreign, and neither is visible in a vial. What makes them tractable is that both are measurable, and the contamination that compounds the risk is measurable too.

That is the whole argument for the weighting. A supplier that publishes purity with a peak list, identity by mass spectrometry, a measured quantity, an endotoxin figure in EU/mL and a microbial screen has answered as much of FDA's sentence as a supplier can answer. A supplier that publishes a purity percentage and a badge has answered the cheapest part of it. The gap between those two positions is worth more than any discount either of them offers.

The supplier costed above, marked against the five factors, with the evidence named so the argument is with the marking rather than the conclusion.

An 86 is not a recommendation to stop reading. It is a claim that five specific rows can be checked in about ten minutes, and the fourteen missing points are itemised above rather than rounded away.

Price is 15 points and it is still worth doing the division, because the neighbouring product sets a reference the reader will meet anyway. Both are Russian heptapeptides in 10 mg lyophilised vials from the same vendor under the same code.

Semax is 26% dearer per labelled milligram and 33% dearer on assayed content. It is tempting to book that premium as the price of the endotoxin and sterility testing, and the documents do not support it: Selank ships under the same two-laboratory arrangement, and its June certificate carries endotoxin, a sterility screen and the same metals panel. Both products score the same way on testing scope for the same reason, and both carry the same lot dependency.

What the premium actually reflects is a different peptide with a different synthesis and a different market, which is a duller answer and the correct one. Anyone comparing across compounds rather than across vendors will find the same method applied at a different price point on our MOTS-c source ranking and our retatrutide source ranking.

A ranking is only honest if it says in advance what would change it.

• Would move it up. An endotoxin and sterility panel on every batch rather than the most recent one, which alone is worth most of the nine missing testing points. Compendial sterility testing to USP Chapter 71 instead of a two-day rapid screen. A named carrier and a transit estimate on the listing itself.
• Would move it down. A new batch shipping with a February-style certificate. Any human-use language appearing in the product copy. A certificate whose lot field stops matching the vials in circulation.
• Would not move it at all. A larger discount, a faster courier, a redesigned product page, more reviews, or a longer trading history. None of those produce a number, and the score is built only from numbers a reader can verify.

Two limits on the whole exercise. A certificate covers a sampled aliquot on a date, and the June endotoxin result was generated on 29 May 2026, before filling, capping and transit. And no score converts research material into a drug product: comparing EU/mL between suppliers is a reasonable way to choose between two research chemicals, and it clears nothing for use in a person. The general method behind this scorecard is set out in our guide to peptide dosing and sourcing references.