Hemolysis — the rupture of red blood cells — is one of the most common reasons blood samples get rejected, and almost all of it is preventable at the point of collection. When red cells break, they release potassium and enzymes that skew results and often force a redraw. Here is what causes hemolysis and how to prevent it.

Why hemolysis matters

A hemolyzed sample often looks pink to red once spun. Because red cells are rich in potassium and certain enzymes, even mild hemolysis can falsely raise potassium, LDH, and AST. The result is rejected samples, delayed reporting, redraws, and potentially misleading values if missed.

Common causes during collection

Most hemolysis comes from technique, not the patient: a needle gauge that is too small (or too large for the vein), a forceful or fast draw, underfilled additive tubes, shaking tubes instead of gentle inversion, repeated probing on a difficult draw, and an over-tight or prolonged tourniquet.

How to prevent it

Match the gauge to the vein — a 21G or 22G for routine draws, a 23G butterfly for small or fragile veins (see 21G vs 23G). Let the vacuum fill tubes at their natural rate, and pull a syringe plunger slowly.

Fill additive tubes to their stated volume, mix by gentle inversion (never shake), release the tourniquet once flow starts, and let alcohol dry before puncture. On tough veins, a controlled butterfly draw beats repeated probing — see small or fragile veins.

Shop supplies

MUDOMED stocks genuine BD Vacutainer® butterfly needles, tubes, and needles with fast U.S. shipping.

For general education only; follow your facility’s protocols.