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General product and regulatory information only, not medical advice. Clinical decisions belong to the treating team and the manufacturer’s instructions for use.
Short answer
A blood warmer is a device that warms blood or plasma before it is given to a patient. Under 21 CFR 864.9205, FDA defines a blood and plasma warming device as one that warms blood or plasma before administration, and it splits the category in two: devices that warm by means other than electromagnetic radiation (Class II) and devices that use radiowaves or microwaves (Class III). Infusion fluid warmers are classified separately.
Definition and scope
The regulation, 21 CFR 864.9205, describes a nonelectromagnetic blood and plasma warming device as one that “warms blood or plasma, by means other than electromagnetic radiation, prior to administration.” The electromagnetic type “employs electromagnetic radiation (radiowaves or microwaves) to warm a bag or bottle of blood or plasma prior to administration.” The rule sits in Part 864, Subpart J, which covers products used in establishments that manufacture blood and blood products (eCFR text via Cornell LII, checked 2026-10-30).
The reason for the device is stated plainly in the research literature: blood warmers “were developed to reduce the risk of hypothermia associated with the infusion of cold blood products” (PLoS One, 2016; PMC5053533, checked 2026-10-30). Searchers also use “IV fluid warmer” for the same idea applied to crystalloid and other infusion fluids; that is a different FDA category, covered below.
How it is used in practice
Both FDA descriptions place the warming step before administration. That is the whole scope of the definition: the device changes the temperature of the product on its way to the patient, and the regulation says nothing more about settings, flow rates or clinical targets. Those details come from each manufacturer’s instructions for use and from the facility’s own policies.
Set temperature is not delivered temperature
A published bench study tested a blood warmer set at 41.5 °C with ten packed red blood cell units (supplied by Hema-Québec) pushed through under a pressure infusion cuff at 150 mmHg and at 300 mmHg. Hemolysis did not increase at either pressure. The outlet temperature, though, was 37.1 °C at 150 mmHg and 33.7 °C at 300 mmHg, and the authors concluded that at 300 mmHg the warmer “does not totally avoid a risk of hypothermia” (PMC5053533, checked 2026-10-30). This is one bench result with one device and one blood source, not patient data, but it shows why the temperature a device is set to and the temperature of what reaches the patient are separate questions.
Types and related concepts
Blood warmer vs IV fluid warmer
FDA’s own classification records (openFDA device classification database, checked 2026-10-30) keep blood warmers and infusion fluid warmers under different regulations and product codes.
| Product code | FDA device name | Class | Regulation |
|---|---|---|---|
| KZL | Device, Warming, Blood and Plasma | 2 | 21 CFR 864.9205 |
| BSB | Warmer, Blood, Non-Electromagnetic Radiation | 2 | 21 CFR 864.9205 |
| BSA | Warmer, Blood, Electromagnetic Radiation | 3 | 21 CFR 864.9205 |
| LGZ | Warmer, Thermal, Infusion Fluid | 2 | 21 CFR 880.5725 (General Hospital panel) |
| LHF | Warmer, Microwave, Infusion Fluid | 2 | 21 CFR 880.5725 (General Hospital panel) |
Note on the infusion fluid rows: the text of 880.5725 defines an infusion pump and does not mention warmers; the database simply files the LGZ and LHF product codes under that regulation number.
The one blood-warmer code that is Class III, BSA, is the electromagnetic one. Under 864.9205(b) that type is subject to premarket approval, and the regulation states that no effective date has been established for that requirement.
Where it matters for labs, clinics and supply decisions
- Classification follows intended use. A device classified as a blood and plasma warmer (864.9205) and one classified as an infusion fluid warmer (LGZ, LHF) fall under different FDA categories, so the labeled intended use is what places a product in one or the other.
- A cabinet is not a blood warmer. Warming cabinets are a separate product type, covered in warming cabinets and their blanket and fluid temperature limits.
- Related devices. The comparison of a fluid warmer with an infusion pump and a pressure device is in what a rapid infuser is; general pump background is in what an IV infusion pump is.
- Context for large-volume transfusion. See massive transfusion protocol for how that setting is defined.
Common misunderstandings
- “Blood warmer and IV fluid warmer are the same product.” FDA files them under different regulations and product codes (table above).
- “The setpoint is the patient’s temperature.” The bench study above measured outlet temperatures 4 to 8 °C below the 41.5 °C setting under pressure, at 150 and 300 mmHg respectively.
- “All blood warmers are regulated the same way.” Electromagnetic (radiowave or microwave) blood warmers are Class III; the other blood-warmer codes are Class II.
Frequently asked questions
What is a blood warmer?
A device that warms blood or plasma before administration, defined in 21 CFR 864.9205. It was developed to reduce the risk of hypothermia from infusing cold blood products.
What is the difference between a blood warmer and an IV fluid warmer?
FDA classifies blood warmers (product codes KZL, BSB, BSA) under 21 CFR 864.9205 and infusion fluid warmers (LGZ thermal, LHF microwave) under 880.5725 in its classification database. The product codes and regulation numbers differ even though both warm a fluid before it reaches the patient.
Is a blood warmer a Class II or Class III device?
Both occur. Nonelectromagnetic blood warmers are Class II (performance standards); electromagnetic radiation blood warmers are Class III (premarket approval).
Sources
- 21 CFR 864.9205, Blood and plasma warming device: https://www.law.cornell.edu/cfr/text/21/864.9205 (checked 2026-10-30).
- 21 CFR 880.5725, Infusion pump: https://www.law.cornell.edu/cfr/text/21/880.5725 (checked 2026-10-30).
- openFDA device classification database, regulation numbers 864.9205 and 880.5725: https://api.fda.gov/device/classification.json?search=regulation_number:864.9205 (checked 2026-10-30).
- Pressure Infusion Cuff and Blood Warmer during Massive Transfusion: An Experimental Study About Hemolysis and Hypothermia. PLoS One, 2016: https://pmc.ncbi.nlm.nih.gov/articles/PMC5053533/ (checked 2026-10-30).
