Your blood contains hundreds of different proteins, each responsible for a specific task. A total blood protein level represents the sum of all these different proteins and the fine balance between protein synthesis and loss that is constantly taking place in your body. A wide variety of medical conditions can lead to low blood protein levels by affecting one or many different proteins.
Normal Blood Protein Levels
Your total protein level is an aggregate measurement of all the proteins in your blood, including enzymes, hormones and transport proteins such as lipoproteins. Albumin, which is synthesized in the liver, normally accounts for over half the protein in your blood, with most of the remainder consisting of a broad mix of proteins classified as globulins. Normal total protein levels can vary slightly between different laboratories but typically fall between 6.3 and 7.9 g/dL, according to the Mayo Medical Laboratories.
Classifying Blood Protein Groups
Low total protein levels, or hypoproteinemia, reflects either a decreased production of protein or increased loss of protein through the urine or stools. This total value reveals very little specific information about the cause of hypoproteinemia, and additional evaluation usually includes an albumin level and serum protein electrophoresis, or SPEP. An SPEP is a laboratory test that involves exposing a small amount of blood placed on specialized paper to an electrical current, which separates the blood proteins into several recognizable groups. Each group can then be measured and the pattern of protein changes evaluated to help narrow down the cause of hypoproteinemia. Albumin makes up one of these groups by itself, in addition to the alpha-1, alpha-2, beta and gamma globulins, according to MedlinePlus.
Low Albumin Levels
Albumin normally accounts for nearly 60 percent of your total blood protein, according to Lab Tests Online. It serves as a common transport protein for many smaller molecules and helps keep the fluid part of your blood from leaking into body tissues and causing swelling. Decreased albumin levels are a common cause of low total blood protein and can occur with many different conditions. Malnutrition, kidney disease with heavy protein loss in the urine, liver disease and chronic inflammatory conditions can all lead to a low albumin. Albumin levels are also commonly lower during pregnancy, due to normal changes in a woman's blood volume.
Low Globulin Levels
Each of the globulin portions seen on an SPEP can also be decreased, either by itself or as part of a broader pattern of changes. Alpha-1 globulins decrease with severe liver disease or a hereditary deficiency of alpha-1 antitrypsin, and alpha-2 globulins are lower with hyperthyroidism, severe liver disease and breakdown of red cells in the circulation. The beta globulins drop with malnutrition and liver cirrhosis. Gamma globulins, which include the antibodies your body uses to fight infection, are lower in various immunodeficiency conditions.
Patterns of Decreased Protein
The relationship between different diseases and the protein changes on an SPEP can guide your health care practitioner in her evaluation. These protein test results, in combination with other signs and symptoms, can help lead to a more specific diagnosis. Any treatment decision will ultimately depend on the underlying condition causing your low protein level.
