Lyophilization
Also known as: freeze-drying · lyo
Lyophilization (freeze-drying) removes water from a frozen product under vacuum, leaving a dry powder or cake that is more stable than a solution.
Lyophilization, or freeze-drying, works in stages. The product is frozen; then, under low pressure, the ice turns directly into vapor (sublimation) in what is called primary drying; then remaining bound water is removed in secondary drying. The result is a dry solid, often called a cake, that is sealed in the vial and later dissolved again (reconstituted) before use.
It is the most common way to make solid forms of protein drugs, because many proteins and peptides are not stable enough in solution to give an acceptable shelf life. Freeze-drying is not gentle by default: the freezing and drying steps themselves can damage proteins, which is why pharmaceutical products are formulated with stabilizing excipients and run on carefully designed cycles. Formulators add stabilizers, called cryoprotectants and lyoprotectants, to protect the protein through freezing and drying. Even after a good process, the dry solid can still have limited long-term stability.
Why it matters
Injectable peptides sold online are commonly lyophilized powders meant for subcutaneous injection, and how well that powder was made and stored affects what you inject. A well-formed, evenly colored cake is a cheap first check. Approved peptide labels tell users to inspect the powder and not use a vial that is discolored or contains particles, and after mixing they expect a clear, colorless solution with no particles.
Freeze-drying improves stability but does not make a product indestructible. How long a given lyophilized peptide keeps its potency depends on the compound, its formulation and its storage, and for most research peptides that has not been tested and published. Treat 'it's freeze-dried, so it lasts' as an assumption, not a fact. And once you add water, the protection that drying gave is gone: from then on the solution's own, usually shorter, stability applies.
How to inspect a lyophilized vial
- Check the seal and cap are intact.
- Look at the cake or powder: it should be uniform in color and free of visible particles.
- Note anything unusual, such as liquid in the vial, a collapsed or melted-looking cake, or discoloration, and do not use a vial that looks wrong.
- Record the lot number and arrival condition before storing the vial as the seller directs.
- Follow any light-protection instruction; the approved tesamorelin product, for example, is stored in its original box to protect it from light.
Common mistakes
- Assuming freeze-dried peptides are stable indefinitely at any temperature.
- Ignoring a discolored, wet-looking or collapsed cake.
- Confusing the stability of the dry powder with the stability of the solution after you add water.
- Assuming a fluffy cake means high purity; appearance says nothing about identity or purity.
- Shaking the vial hard when reconstituting; approved peptide labels call for gentle swirling.
Sources
- ReviewLyophilization and development of solid protein pharmaceuticals. Int J Pharm, 2000. PMID 10967427.
- ReferenceAnalysis of illegal peptide drugs via HILIC-DAD-MS. Talanta, 2017. PMID 28738623.
- Prescribing informationEGRIFTA WR (tesamorelin) for injection - prescribing information and instructions for use. DailyMed, U.S. National Library of Medicine, 2025.
Page updated . How we grade evidence: methodology.
Related Terms
Cold Chain
Cold chain is the unbroken control of temperature for a temperature-sensitive product, from manufacture through shipping and storage to use.
Reconstitution
Reconstitution is dissolving a freeze-dried (lyophilized) powder in a measured volume of liquid to make a solution of known concentration for injection.
Vial Shelf Life
Vial shelf life ends at the earlier of the original expiration date and the applicable limit after opening or mixing.
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