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Short answer
Cryopreservation media are the solutions cells are suspended in before freezing. Per Thermo Fisher’s Gibco guidance, a freezing medium typically combines a base medium, a cryopreservative such as DMSO or glycerol, and a protein source. The formulations in use differ mainly in cryoprotectant percentage (5% to 10%) and in whether the protein source is serum, BSA or absent.
Definition and scope
In cell culture, “cryopreservation medium” or “cell culture freezing media” means the liquid in which cells are held for freezing and long-term storage, as distinct from the growth medium used while cells are expanding. The term covers laboratory-made mixtures built from a growth medium plus additives, and ready-to-use commercial products. This page compares the formulations that two primary sources describe. For the handling workflow itself, see the cryopreservation basic protocol and best practices guide; this page does not repeat it.
What is in a freezing medium?
Thermo Fisher’s Gibco cell culture basics describes three parts.
Base medium
Usually the cell line’s own complete growth medium, or a fresh serum-free medium for serum-free lines.
Cryopreservative (cryoprotectant)
DMSO or glycerol. ATCC’s Animal Cell Culture Guide states that glycerol and DMSO at 5% to 10% are the most common cryoprotectants. For the properties of DMSO itself, see DMSO molar mass and related data.
Protein source
Serum in the complete medium, or cell culture-grade BSA in the serum-free recipe Gibco describes, or none in a chemically defined, protein-free product.
Cell culture freezing media: the formulations compared
Every row below is a formulation stated by Thermo Fisher Gibco or ATCC. Percentages are as those sources give them.
| Medium type | Stated composition | Source |
|---|---|---|
| Serum-containing, DMSO | Complete medium containing 10% DMSO | Thermo Fisher Gibco |
| Serum-containing, glycerol | Complete medium containing 10% glycerol | Thermo Fisher Gibco |
| ATCC standard | 5% DMSO in complete growth medium (“most ATCC cell lines”) | ATCC |
| Serum-free, lab-made | Fresh serum-free medium with 7.5% DMSO and 10% cell culture-grade BSA | Thermo Fisher Gibco |
| Conditioned/fresh serum-free mix | 50% cell-conditioned serum-free medium with 50% fresh serum-free medium containing 7.5% DMSO | Thermo Fisher Gibco |
| Conditioned/fresh complete mix | 50% cell-conditioned medium with 50% fresh medium containing 10% glycerol or 10% DMSO | Thermo Fisher Gibco |
| Premade, protein-free | Chemically defined, protein-free, sterile cryopreservation medium with 10% DMSO | Thermo Fisher Gibco |
| Premade, serum-free | ATCC Serum-Free Cell Freezing Medium: 10% DMSO and methylcellulose | ATCC |
Two points stand out. First, the same cryoprotectant appears at 5%, 7.5% and 10% depending on the source and the medium, so there is no single “standard” DMSO concentration. Second, going serum-free changes the protein source rather than removing the need for one: the lab-made serum-free recipe adds BSA, while premade products supply their own defined formulation.
Where it matters for labs and supply decisions
Ready-to-use commercial products, such as the Gibco and ATCC premade media in the table, stand in contrast to the lab-made recipes above. A label or product sheet can therefore be read against the three-part framework:
- Which cryoprotectant, and at what percentage?
- What is the protein source: serum, BSA, methylcellulose or none (protein-free)?
- Is it sterile and ready to use, or a mixture to be prepared?
Thermo Fisher states that lab-prepared freezing medium should be stored at 2 to 8 °C until use, and advises following the cell line and product-specific instructions closely. ATCC reports a working density of 1×106 to 5×106 viable cells/mL and a slow cooling rate, generally −1 °C per minute; Gibco gives approximately 1 °C per minute. These are general figures, so the supplier’s sheet for the specific cell line governs. Gibco advises storing frozen cells in the gas phase above liquid nitrogen, below −135 °C, and warns of an explosion hazard with glass and plastic cryovials in liquid-phase storage; see liquid nitrogen and cryogen handling safety and what a cryovial is for the containers.
For media that avoid animal-derived components, see the dictionary entry on xeno-free media, and for the growth-medium side of the serum question, serum-free vs serum-containing cell culture media.
Common misunderstandings
“Freezing medium is just growth medium with DMSO.”
That describes the serum-containing case. Gibco’s serum-free recipe adds BSA, and premade products are defined formulations of their own.
“10% DMSO is the standard.”
ATCC states that most of its cell lines are frozen in 5% DMSO with complete growth medium, while Gibco’s example formulations use 10% or 7.5%. The right concentration is the one the cell line’s supplier specifies.
“Glycerol and DMSO are interchangeable.”
Both are listed as common cryoprotectants, and Gibco gives glycerol as an alternative at 10%, but neither source presents them as freely swappable for every line; follow the line-specific instructions.
Frequently asked questions
What is cryopreservation medium made of?
A base medium, a cryopreservative (DMSO or glycerol) and a protein source, according to Thermo Fisher Gibco.
What is cell culture freezing media?
It is the same thing: the medium cells are suspended in for freezing, as opposed to the medium used for growing them.
Can freezing medium be bought ready-made?
Yes. Gibco describes a chemically defined, protein-free, sterile medium with 10% DMSO and a ready-to-use complete medium, and ATCC lists a serum-free freezing medium with 10% DMSO and methylcellulose.
Sources
- Thermo Fisher Scientific, Gibco Cell Culture Basics, “Freezing cells”: thermofisher.com (checked 2026-10-29).
- ATCC, Animal Cell Culture Guide: atcc.org (checked 2026-10-29).
