Why is Hemoglobin Higher in Peripheral Blood Compared to Venous Blood?

The peripheral regions generally refer to capillaries. The hemoglobin concentration in the peripheral regions is higher than that in veins because veins have lymphatic return, and the blood circulation speed in capillaries is slower than that in veins. The human body includes blood circulation and lymphatic circulation, which are connected through lymphatic vessels and veins. Lymph in lymphatic vessels originates from body tissue fluid and has a lower hemoglobin content than blood. When it returns to the blood through veins, it produces a slight diluting effect. Capillaries have no lymph at their ends, so the blood is not diluted, and the hemoglobin concentration is higher than that in venous blood. Capillaries are located at the ends of limb blood vessels. When the temperature is low, blood circulation is poor, and blood concentration increases. The number of hemoglobin in the same unit of blood will increase relatively, but the deviation from the venous blood value is not significant.

Blood routine tests primarily use materials from the peripheral blood or venous blood of subjects. Peripheral blood is usually collected at the fingertips, where there are many interfering factors, and the test values may deviate. If the fingertip blood test results are abnormal, a venous blood test is usually required for reexamination. It is recommended to use venous blood for blood routine tests when confirming a diagnosis.