Hemoglobin
What it measures, and what changes the number.
Hemoglobin is the iron-containing protein inside red blood cells that carries oxygen from the lungs to the tissues. This test measures its concentration in whole blood and is a core part of the complete blood count.
It is read with Hematocrit and the Red blood cells count, and with indices such as MCH and MCHC that describe how much hemoglobin each cell holds. Iron studies such as Ferritin are often ordered on the same request because iron is needed to build hemoglobin.
The result can shift with hydration, body position during the draw, and how long the tourniquet was applied. Capillary finger-prick samples can differ from venous samples. Living at altitude and smoking also influence the value. The sample is collected in an anticoagulant tube and should be mixed well before analysis. Labs may print it as Hemoglobina.
Often read alongside: Hematocrit, Red blood cells, MCH, MCHC, Ferritin