In an undiluted specimen, count and differentiate red cells and white cells at the same time. You can count red cells on a hand counter and use the differential counter for white cells.

If you cannot differentiate white cells from red cells in the undiluted specimen, a plain capillary tube may be filled with crystal violet acetic acid diluent which is subsequently expelled from the tube. A very thin coating of the diluent will remain on the inside of the tube. CSF is drawn halfway up into the tube, which is then rocked back and forth to mix. The hemacytometer is then filled with the fluid containing stained white blood cells and lysed red cells.

If cells are numerous and overlapping and it is necessary to focus through several planes in order to see all of the cells, a dilution must be made.

When macroscopic appearance is turbid, milky or bloody, a significant dilution is usually necessary.