Globulin

Your blood carries dozens of proteins, and they fall into two groups. Albumin, more than half, is made by your liver: it keeps fluid in the vessels and carries hormones, fatty acids and medicines. Everything that is not albumin is together called globulin, and that is a mixed company: transport proteins such as transferrin for iron and the proteins that bind thyroid hormone and sex hormones, clotting proteins, the proteins that rise during inflammation, and the antibodies, the immunoglobulins, which your immune system makes and which form the largest part. Globulin is not measured separately. Your total protein and your albumin are determined, and the difference is the globulin fraction. That has a consequence: every movement in the total that does not come from albumin lands in globulin, and the number does not say which of the dozens of proteins it was. Anyone who wants to know has a protein electrophoresis done, which splits the fraction into alpha, beta and gamma, or has the antibodies measured separately as IgG, IgA and IgM. Your report prints globulin in g/L, or you calculate it yourself with the calculator on this page. Because it is a subtraction, nobody publishes a band for it; calculated from the middle of the bands for total protein and albumin, a healthy adult comes out around 26.5 to 33.5 g/L. Anyone who drinks normally and has no inflammation usually sits in there.

Albumin and globulin come from different corners of your body. Albumin is made by your liver; the largest part of the globulins is made by your immune system. The split therefore shows which side is moving, and that is precisely what total protein hides: a normal total can conceal a falling albumin that is filled up by a rising globulin, the picture of a long-standing inflammation or a liver disease. The second reason is that a high globulin is one of the few clues in ordinary blood to an inflammation or infection that has been smouldering for months, or to a liver that is forming scars and in which the antibodies rise. Rarely the reason is a single cell line in the bone marrow making one abnormal protein in large quantities, and then the protein electrophoresis is the test that shows it. The honest limitation is that globulin is a coarse number. It responds most strongly to how concentrated your blood was that morning: arriving dehydrated at the draw lifts it, drinking a lot lowers it, and that is by far the most common explanation for an outlier. There is no band, so your own course is the reference point, and the meaning lies in what albumin and total protein do beside it.

A low globulin usually means your blood was diluted. The most common explanation first: dilution by fluid, after drinking a lot, an infusion or in pregnancy, where albumin and total protein fall just as hard; protein loss through the kidneys, where mainly the smaller globulins leak away together with albumin and the urine foams; and rarely an immune system that makes too few antibodies, inborn or through medicines, with recurring infections as the hallmark. A low globulin with a normal albumin is almost always harmless. A high globulin means a concentrated sample or more protein from the immune system. Usually it is the first and rarely the last: dehydration, where albumin rises just as hard and the ratio stays the same; a long-standing inflammation or infection, where the immune system makes antibodies and inflammatory proteins for months while albumin falls; a chronic liver disease, where the antibodies rise because the liver clears them less; and rarely an abnormal protein from a single cell line in the bone marrow, visible as a peak on a protein electrophoresis. Read globulin beside albumin and total protein, because the question is which half moved, beside CRP and ESR, which show whether an inflammation is at play, and beside the albumin/globulin ratio, which says independently of your fluid balance how the two relate.