Peptide pens explained: how prefilled research pens are built and labelled

What is a peptide pen?

A peptide pen is a pen-shaped device holding a sealed cartridge, usually of peptide solution. In a prefilled pen, also sold as a pre-mixed pen, the solution is normally already in the cartridge when the pen is made, so there is no powder to dissolve first. Some designs instead keep a freeze-dried powder and its liquid apart in a two-chamber cartridge. All the pens discussed in this guide are supplied with the solution already in the cartridge. For background on the molecules themselves, see what peptides are.

Two other terms are common. A prefilled pen is often called disposable, because it is not refilled once its cartridge is empty, while a reusable pen is an empty device that takes separate cartridges. The pens in this guide are all prefilled.

Inside the pen: cartridge, plunger and drive mechanism

Most prefilled pens share the same basic layout, whatever compound is inside: a cartridge that holds the solution and a drive mechanism behind it.

Labelled content versus concentration

The milligram figure on a single pen, such as 10mg or 40mg, is its labelled content: the total mass of compound in that one pen. (Pack names can show a total for more than one pen; see below.) It is not a concentration. Concentration is the amount of compound in each millilitre of solution: the content divided by the volume. The NIST guide to SI units defines this mass concentration as the mass of the substance divided by the volume of the solution.

As plain arithmetic, 6 mg in 3 mL is 2 mg/mL, while 6 mg in 1.5 mL is 4 mg/mL, so two pens with the same labelled content can have different concentrations. Where a label prints the fill volume next to the content, both figures are known. Where it does not, the label alone does not give the concentration, and a figure published for a different product or pen model should not be assumed to apply.

Pack totals are a third kind of figure. The NAD+ double pen is sold as 1000mg, made up of two pens that contain 500mg each. NAD+ is a coenzyme rather than a peptide, but it is supplied in the same pen format. For freeze-dried vials, where the concentration depends on the volume of liquid a laboratory adds, the peptide calculator does the same content-divided-by-volume arithmetic.

Single-compound, blend, bundle and double pens

The pens in this range come in four arrangements, each labelled differently.

A single-compound pen is the simplest case: one compound, one cartridge, one labelled content. A blend pen mixes more than one compound in the same solution, so its headline figure is the sum of the parts. Where the maker states each compound's share, the product description gives it: the 40mg BPC-157 + TB-500 blend pen holds 20mg of each. Once mixed, the compounds share one solution, and the blend is a different product from either compound alone, with its own label and documents.

A bundle keeps compounds apart. The BPC-157 + TB-500 bundle is two separate 10mg pens, each with its own cartridge and label, so any lab report has to match each pen's own product, strength and batch. A report for one pen does not cover the other. The NAD+ double pen is two identical pens sold together as one pack.

Peptide pen vs vial

Research peptides are also supplied in glass vials, usually as a freeze-dried (lyophilised) powder under a rubber stopper. The two formats differ in labelling, handling and paperwork.

In handling terms a pen is self-contained: the solution is made up and sealed into its cartridge when the pen is filled. A vial of powder has no solution until a laboratory prepares one, so storage guidance for a powder in a vial does not carry over to a solution in a pen. Likewise, a report on a vial does not describe a pen of the same compound: the format, the solution and usually the batch differ.

What the label and batch documents should state

A pen label is small, so the details that identify a pen and connect it to its paperwork are spread across the pen, its carton and the product documents. Together they should give:

• the compound name and, for a blend, each compound and, where stated, its share of the total
• the labelled content per pen, and the pack total where a pack holds more than one pen
• the fill volume or concentration, where the manufacturer states it
• a batch or lot number
• an expiry or retest date
• storage conditions
• a research-use statement

Batch documents sit alongside the label. A certificate of analysis should name the laboratory, the sample it received, the batch number, the methods used (typically HPLC for purity and mass spectrometry for identity) and the date of testing.

Laboratories accredited to ISO/IEC 17025, the international standard for testing and calibration laboratories, have been assessed against requirements for competence, impartiality and consistent operation. Accreditation is held by a particular laboratory, so a claim of it can be checked with the accreditation body; in the UK, UKAS keeps a searchable directory of the organisations it accredits.

A report covers the identified tested sample only. It should match the pen by product, strength and batch, and a report for a single-compound pen does not cover a blend or a bundle that contains the same compound. The peptide lab reports page lists the published reports matched to each product. Of the pens named in this article, only the NAD+ double pen has a published report so far; the BPC-157 10mg pen, the TB-500 10mg pen, the BPC-157 + TB-500 blend pen and the bundle do not yet have one. The guide to peptide testing and certificates of analysis explains how to read one.

Storage in brief

Storage is whatever the label and product documentation state for that pen. A prefilled pen holds a solution, so guidance written for freeze-dried powder does not apply to it. The BPC-157 10mg pen's label, for example, says to store it at 2–8°C (refrigerated) and not to freeze it or expose it to sunlight; conditions like these apply to the pen as supplied. Keeping a pen in its carton keeps it out of the light and keeps any batch details printed on the carton with the pen. More detail is in the guide on how to store peptide pens.

Disposing of unwanted or expired pens

An unwanted, emptied or expired pen is a mix of materials: the cartridge, the plastic housing and the parts of the mechanism, plus whatever solution is left in the cartridge. It does not belong in household waste or recycling.

Research pens are laboratory waste. Guidance for England on GOV.UK, from the Environment Agency and Defra, says waste must be identified and classified before it is sent for recycling or disposal. Laboratories then pass it to their usual waste contractor.

Regulatory and anti-doping status

BPC-157 and TB-500 are not licensed medicines in the UK. US Food and Drug Administration briefing documents for its July 2026 compounding advisory committee found no approved product containing BPC-157 in any country, and no approved TB-500 product in the United Kingdom.

There is no UK-licensed NAD+ medicine either. When checked on 22 October 2026, the MHRA's index of active substances in UK medicines had no entry for BPC-157, TB-500, thymosin beta-4 or NAD+ (nicotinamide adenine dinucleotide). The pens described here are supplied for laboratory research only; they are not licensed medicines and have not been authorised by the MHRA.

Under the 2026 Prohibited List of the World Anti-Doping Code, in force from 1 January 2026, BPC-157 is named in class S0. That class covers pharmacological substances that no other section of the List addresses and that have no current approval by any governmental regulatory health authority for human therapeutic use. Class S2.3 names "Thymosin-β4 and its derivatives e.g. TB-500". Substances in both classes are prohibited at all times.

WADA has published the 2027 List, which takes effect on 1 January 2027. According to the US Anti-Doping Agency's summary, it keeps BPC-157 under S0 and TB-500 under S2.

NAD+ is not named on the 2026 List. That does not by itself make it permitted: WADA says most categories give only common examples and are not exhaustive, and the List covers prohibited methods as well as named substances. The full List, and UK Anti-Doping in the UK, remain the references.