Written and maintained by CASRAI Editorial Board
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This page describes products and general use; it is not medical advice.
A microhematocrit centrifuge is a small, high-speed bench centrifuge built to spin sealed capillary tubes of blood so the red cells pack at one end and the hematocrit (the percentage of the column that is red cells) can be read from a scale. Clinic and laboratory staff, buyers and students use this page to see what the machine consists of, how two manufacturer examples differ, and how the reader that comes with it works.
What a microhematocrit centrifuge is
It is a centrifuge designed for the separation of microhematocrit samples. One manufacturer manual describes its unit as a high-speed (11,000-12,000 RPM) centrifuge for exactly that purpose; another says its unit is designed exclusively for standard microhematocrit capillary tubes and not for microcentrifuge or conical tubes. The same machine is also called a hematocrit centrifuge.
In US federal regulation the centrifuge is one part of a larger device. 21 CFR 864.6400 defines a hematocrit measuring device as “a system consisting of instruments, tubes, racks, and a sealer and a holder.” It is Class II (special controls) and exempt from premarket notification, subject to the limitations in 21 CFR 864.9 (eCFR, checked 2026-10-30). The centrifuge, the capillary tubes, the sealer and the holder or reader are therefore treated as one measuring system.
How it is built
The two manufacturer manuals cited on this page describe the same basic layout:
- Rotor. A 24-place rotor in the UNICO C-MH30, with a replaceable rubber ring (gasket) against which the sealed end of each tube rests.
- Lid. A screw-down metal lid on the UNICO model, and a lid safety switch that shuts off the motor when the lid is lifted; the unit also uses electric motor braking.
- Timer. A mechanical 5-minute timer with a bell on the UNICO model; an adjustable 1-7 minute timer (3 minutes by default) on the MPD Scientific CH1345.
- Reader. A separate scale with a slider, used after the spin (see below). The C-MH30 includes one; the CH1345 package list names sealing putty or a rubber sealing disc, the rotor and a power cord.
Types and variants
| Variant | Typical use | Key difference (source) |
|---|---|---|
| Mechanical-timer model, nominal speed | Spinning up to 24 sealed microhematocrit tubes | Nominal 11,500 RPM with 24 filled tubes; maximum speed depends on the number and fill volume of tubes; 5-minute mechanical timer with bell (UNICO C-MH30 manual) |
| Fixed-speed model, adjustable timer | Standard 75 mm microhematocrit tubes only | Fixed 12,000 rpm; timer 1-7 minutes, 3 minutes default (MPD Scientific CH1345 manual) |
Hematocrit reader and reader card
The “microhematocrit reader” and “hematocrit reader card” are the scale used after spinning, not a separate centrifuge type. Per the UNICO manual, the reader has a slider (capillary holder), an indicator lever, a zero line, a 100% line and a scale.
Specifications that matter
| Specification | UNICO C-MH30 | MPD Scientific CH1345 |
|---|---|---|
| Speed | Nominal 11,500 RPM with 24 filled tubes | Fixed 12,000 rpm |
| Timer | Mechanical, 5 minutes, bell | 1-7 minutes, 3-minute default |
| Rotor | 24-place | Do not exceed rotor capacity |
| Tubes | Sealed end rests against the rotor gasket | Standard 75 mm x 1.1-1.2 mm bore; heparinized tubes for blood without anticoagulant, plain tubes for anticoagulated blood |
| Lid | Screw-down; safety switch | Not to be opened while the rotor is moving |
How the hematocrit reader works
After the spin, the sealed capillary tube is placed in the reader, a separate scale supplied with the centrifuge. Per the UNICO manual, the reader has a slider (capillary holder), an indicator lever, a zero line, a 100% line and a scale: the packed red cell column and the plasma column in the tube are lined up against the zero and 100% lines, and the indicator marks the boundary between red cells and plasma so the percentage can be read from the scale. The manual describes the reader as designed to make hematocrit reading fast, easy and accurate.
Why a spun hematocrit can differ from an analyzer value
The same manual says a spun hematocrit “cannot be expected to correlate exactly with every method,” that automated CBC hematocrits “will not generally correlate” with centrifuged ones, and that control values should be used for spun hematocrits. For the tubes themselves, see What Is a Capillary Tube?; for the collection side, see capillary blood collection.
Safe use and handling basics
- Seal tubes before loading and load a balanced rotor; do not exceed rotor capacity (MPD Scientific manual).
- Use tubes rated for the unit’s speed and inspect them for cracks (MPD Scientific manual).
- Screw the lid down snugly; if it is not snug tubes could break, and it must not be over-tightened (UNICO manual).
- Open the lid only after the rotor has come to a complete stop (UNICO manual); never open it while the rotor is in motion (MPD Scientific manual).
- Wear gloves, lab coat and eye protection, treat blood as potentially infectious, and handle used tubes as sharps waste (MPD Scientific manual). See red bag waste for the OSHA background on regulated waste.
- Tube breakage during a spin can generate aerosols, which is why the MPD Scientific manual has a dedicated breakage section; follow the manufacturer manual and your facility protocol.
Common mistakes
- Lid not snug, so tubes can break (UNICO manual).
- Unbalanced or overfilled rotor (MPD Scientific manual).
- Using non-rated tubes, or microcentrifuge or conical tubes in a unit designed only for microhematocrit capillary tubes (MPD Scientific manual).
- Comparing a spun hematocrit directly with an analyzer hematocrit without allowing for method differences (UNICO manual).
FAQ
Is a hematocrit centrifuge the same as a microhematocrit centrifuge?
Manufacturer manuals use the terms for the same machine: a high-speed centrifuge for sealed microhematocrit capillary tubes. The FDA regulation uses the broader term “hematocrit measuring device” for the whole system.
What is a hematocrit reader card?
It is the scale used to read the packed-cell percentage after centrifugation. In the UNICO manual it consists of a slider, indicator lever, zero line, 100% line and scale.
Why does a spun hematocrit differ from an analyzer result?
The UNICO manual states that the two methods will not generally correlate exactly and that control values should be used for spun hematocrits.
Sources
- 21 CFR 864.6400, Hematocrit measuring device, eCFR, checked 2026-10-30: ecfr.gov
- UNICO C-MH30 Micro-hematocrit Centrifuge Operation Manual, United Products & Instruments, checked 2026-10-30: manual (PDF)
- MPD Scientific CH1345 User Manual, checked 2026-10-30: manual (PDF)
Related: HemoCue, a point-of-care hemoglobin method, and biohazard specimen bags.
