Capillary hemoglobin is higher than venous blood because of the lymphatic return in venous blood.
In addition to blood circulation in the normal human body there is also lymphatic circulation, in which the lymphatic fluid is derived from tissue fluid, absorbed through the capillary lymphatic vessels, mainly to recover the larger proteins in the tissue fluid and a small number of red blood cells leaking from the blood, so the lymphatic fluid contains very little hemoglobin.
The lymphatic fluid flows back into the veins through the lymphatic vessels, where the lymphatic fluid with less hemoglobin mixes with the venous blood resulting in venous blood hemoglobin that is slightly lower than that of the capillaries, but the difference is not great.
If there is a large difference between capillary hemoglobin and venous blood, please go to the hospital immediately to avoid delay.