Total protein measurements can reflect nutritional status and may be used to screen for and help diagnose kidney disease, liver disease, and many other conditions. Sometimes conditions are first detected with routine testing before symptoms have begun to appear. If total protein is abnormal, further tests must be performed to identify which specific protein is abnormally low or high so that a specific diagnosis can be made.

A total protein test is one component of a Comprehensive Metabolic Panel (CMP) that is often ordered as part of a routine health checkup. Total protein may also be ordered to provide general information about your nutritional status, such as when you have undergone a recent weight loss. It can be ordered along with several other tests to provide information if you have symptoms that suggest a liver or kidney disorder or to investigate the cause of abnormal pooling of fluid in tissue (edema).

Results of a total protein test will give your doctor information on your general health status with regard to your nutrition and/or conditions involving major organs, such as the kidney and liver. However, if results are abnormal, further testing is usually required to help diagnose the disease affecting protein levels in the blood.

Low total protein levels can suggest a liver disorder, a kidney disorder, or a disorder in which protein is not digested or absorbed properly. Low levels may be seen in severe malnutrition and with conditions that cause malabsorption, such as Celiac disease or inflammatory bowel disease (IBD).

High total protein levels may be seen with chronic inflammation or infections such as viral hepatitis or HIV. They may be caused by bone marrow disorders such as multiple myeloma.

Some laboratories also report the calculated ratio of albumin to globulins, termed the A/G ratio. Normally, there is a little more albumin than globulins, giving a normal A/G ratio of slightly over 1. Because disease states affect the relative changes in albumin and globulins in different ways, this may provide a clue to your doctor as to the cause of the change in protein levels. A low A/G ratio may reflect overproduction of globulins, such as seen in multiple myeloma or autoimmune diseases, or underproduction of albumin, such as occurs with cirrhosis, or selective loss of albumin from the circulation, as occurs with kidney disease (nephrotic syndrome). A high A/G ratio suggests underproduction of immunoglobulins as may be seen in some genetic deficiencies and in some leukemias. More specific tests, such as albumin, liver enzyme tests, and serum protein electrophoresis must be performed to make an accurate diagnosis.

Prolonged application of a tourniquet during blood collection can result in a blood sample that has a higher protein concentration than the rest of the circulation. This will mean that the test result for total protein will be falsely elevated (higher than the actual concentration in the circulation).

Drugs that may decrease protein levels include estrogens and oral contraceptives.