Unfractionated Heparin Level

Method Name

Chromogenic/Inhibition of Factor Xa


Unfractionated Heparin Level; Heparin Level; UFH; Anti-Xa (UFH), Heparin Level (Unfractionated)

Specimen Required

One full 2.7 mL blue top tube (3.2% sodium citrate). Specimen will be rejected if the tube is underfilled or overfilled.

Specimen Minimum Volume

2.7 mL of blood

Specimen Stability Information

Specimen is stable for 1 hour at room temperature. Platelet-poor plasma is stable for 4 hours. Stability can be extended to 2 weeks if platelet poor plasma is frozen at -20 degrees C.

Performing Laboratory

As ordered. Turn around time is 4 hours.

Reference Values

Therapeutic Range = 0.3 – 0.7 IU/mL