Why should you choose lithium heparin as the additive when electrolytes are requested?

Sodium heparin may affect the sodium level in the sample. Lithium has a low interference level with tests of other ions. It also prevents the blood from clotting or turning into a solid. The lithium heparin then helps to produce a whole blood sample, instead of a clotted one, which is better for testing.

One would use either lithium, sodium, or ammonium heparin, depending on the nature of the blood sample. Lithium samples would contain a green top. Each of the color tops would indicate a different type of heparin.