Total proteinSerum total protein
All the protein circulating in your blood, mostly albumin and antibodies.
Total protein is the combined concentration of every protein in the liquid part of your blood. Two families make up almost all of it: albumin, which the liver makes, and the globulins, which include antibodies made by the immune system.
It matters as a starting point rather than an answer, because the total can look normal while its two halves are both abnormal in opposite directions. That is why reports print albumin and globulin separately, and why the ratio between them carries more information than the sum.
In practice it is interpreted through its components: a low albumin with a normal total points somewhere quite different from a raised globulin with a normal total. Dehydration raises the whole figure by concentrating it.