Tesamorelin is a synthetic peptide that comes as a white lyophilised powder, stores at −20 °C long-term, and a legitimate COA will show purity above 98% confirmed by HPLC. Those three facts answer most of what researchers ask about it.
What Is Tesamorelin
Tesamorelin is a 44-amino-acid analogue of human growth hormone-releasing hormone (GHRH). It has a well-established analytical profile from its pharmaceutical development history, which makes reading a COA for tesamorelin more straightforward than for less-studied peptides.
It is sold for research as a lyophilised — freeze-dried — powder, typically in vials of 2 mg, 5 mg, or 10 mg, though 20 mg vials are also common for bulk research use.
Tesamorelin Storage Temperature
Store unreconstituted tesamorelin powder at −20 °C. That is a standard lab freezer, not a −80 °C ultra-low unit. At −20 °C, properly sealed vials remain stable for an extended period from the date of manufacture.
A few practical points:
- Keep vials away from repeated freeze-thaw cycles. Each cycle stresses the peptide structure. Pull out what you need and put the rest straight back.
- Short-term storage at 2–8 °C (a regular fridge) is fine for up to four weeks if the vial is sealed and dry.
- Once the powder has been taken into solution, store at 2–8 °C and use within 28 days. Do not freeze a peptide solution.
Tesamorelin Powder Storage
The enemy of lyophilised peptide is moisture, not just heat. Tesamorelin powder absorbs water from the air readily. Once water gets in, hydrolysis — meaning water molecules break chemical bonds in the peptide chain — can degrade the compound even at low temperatures.
Practical rules:
- Keep vials sealed and in their original packaging until use.
- If you transfer vials between locations, let them come to room temperature before opening. That prevents condensation forming inside the vial when you pull the cap.
- Store in a dry environment. A small silica gel packet inside a sealed container works well if your freezer runs humid.
- If a vial looks clumped or discoloured rather than fine white powder, moisture has likely entered.
Tesamorelin Purity and What the Numbers Mean
Tesamorelin purity describes what fraction of the material in the vial is actually tesamorelin, as opposed to residual solvents, synthesis by-products, or degraded fragments. It is expressed as a percentage by HPLC — high-performance liquid chromatography, a method that separates compounds by how they move through a column and measures each peak.
Tesamorelin 99% purity means HPLC found 99% of the sample to be the target compound. That is considered research grade. Most well-tested batches come in at 98–99%+.
What makes up the remaining 1–2%? Usually small amounts of:
- Truncated sequences — peptide chains where synthesis stopped one amino acid short
- Oxidised methionine residues — a common side-reaction during synthesis
- Residual acetate from the purification step
None of these are dangerous at trace levels, but they matter for research reproducibility. A sample at 95% purity is not the same experimental tool as one at 99%.
How to Read a Tesamorelin COA
A COA — certificate of analysis — is the lab report issued after a batch is tested. It should come from a third-party analytical laboratory, not from the peptide manufacturer themselves.
A complete tesamorelin COA will include:
| Test | Method | What to look for |
|---|---|---|
| Identity | Mass spectrometry | Molecular weight matches 5135.8 Da |
| Purity | HPLC (UV at 214 nm) | ≥ 98%, ideally 99%+ |
| Water content | Karl Fischer titration | Typically < 8% for lyophilised peptides |
| Residual solvents | Gas chromatography | Should be present only at trace levels within accepted limits |
| Appearance | Visual | White to off-white powder |
For a tesamorelin 20 mg COA, check that the batch number on the vial matches the batch number on the document. A COA without a batch number cannot be matched to a specific lot and is not useful.
The molecular weight is the fastest identity check. Tesamorelin is 5135.8 daltons. If the mass spec result on the COA does not land within 1 dalton of that, something is wrong.
Practical Summary
Tesamorelin powder stores at −20 °C long-term and at 2–8 °C for up to four weeks. Protect it from moisture at every stage. On the COA, look for HPLC purity at 98% or above, a mass spec result near 5135.8 Da, and a batch number you can match to the vial. Those checks take about two minutes and tell you most of what you need to know about a batch before you use it.
NXT Labs products are sold strictly as research chemicals for in vitro research, laboratory testing and analytical purposes only, and are not intended for use in any human or animal application.
NXT Labs supplies research peptides for laboratory use. Browse the full range or view current Certificates of Analysis.
