Preparation of Blood Smears

ALI staff often need to review smears made from the blood drawn for a CBC. Although not required, a properly prepared blood smear may be useful for specimens that will be more than 12 hours old when received.

The following instructions will assist you in the preparation of blood smears. Address any questions or concerns to the ALI Hematology Supervisor.


Pre-cleaned frosted glass slides, plain capillary tubes or applicator stick, and cardboard slide holders.



  1. Label a clean, dust-free slide with the patient's full name and the date.

  2. Using a plain capillary tube or applicator stick, place a drop of well-mixed blood 2-3 mm in diameter on the slide as illustrated.

  3. Hold the end of a second slide (spreader slide) against the surface of the first slide at an angle of 30 40 degrees; slide it back to make contact with the drop of blood.

  4. By capillary action, the blood will run across the end of the spreader slide.

  5. Quickly, smoothly, and evenly, move the spreader slide away from the drop. The resulting blood smear should be at least two-thirds of the length of the slide.

  6. The smear should have an even "feathered edge." Allow the smears to air dry completely. Once the smears are dry, place them in the cardboard slide holders, tape shut, and transport to ALI along with the EDTA blood.