A protein blood test measures the amount of protein in the blood. Protein levels may be high or low due to malnutrition, dehydration, infections such as bacterial endocarditis, or conditions such as multiple myeloma.
Proteins are important for the body to function properly. They help fight disease, regulate body functions, build muscle, and carry substances throughout the body.
A total protein blood test may help diagnose kidney disease, liver disease, and other conditions. If results are abnormal, more tests may be needed to identify which protein is altered.
Reference values
The reference values for people aged 3 years and older are:
- Total protein: 6.0 to 8.3 g/dL
- Albumin: 3.5 to 5.0 g/dL
- Globulin: 2.0 to 4.0 g/dL
These values are only a guide and may vary slightly between laboratories.
Protein levels are measured in the serum obtained from a blood sample. Fasting is usually not necessary for this test, but it may be required if it is done together with other blood tests. Always follow the instructions provided by the laboratory or your healthcare professional before having your blood drawn.
When it is ordered
A total protein blood test may be done as part of a routine check-up. According to the NHS, this test can help diagnose conditions such as kidney disease, liver disease, and malnutrition. It may also be ordered after recent weight loss or to investigate fluid buildup in the tissues.
In some cases, protein fractions are also measured. This test separates blood proteins into two main groups: albumin and the remaining proteins, most of which are globulins, to support a more precise diagnosis.
What results mean
Changes in protein levels may indicate certain conditions, depending on which proteins are affected.
1. Low total protein
Possible causes of low blood protein levels include:
-
Chronic alcohol use disorder
-
Liver disease, which can affect albumin and globulin production in the liver
-
Kidney disease, due to protein loss in the urine
-
Pregnancy
-
Overhydration
-
Cirrhosis
-
Hyperthyroidism
-
Calcium and vitamin D deficiency
-
Heart failure
-
Malabsorption disorders
In addition, severe malnutrition can also lead to low protein levels in the blood.
2. High total protein
Possible causes of high blood protein levels include:
-
Increased antibody production in some infectious diseases
-
Cancer, especially multiple myeloma and macroglobulinemia
-
Autoimmune diseases, such as rheumatoid arthritis and lupus
-
Granulomatous diseases
-
Dehydration, because blood plasma becomes more concentrated
-
Hepatitis B, hepatitis C, and autoimmune hepatitis
-
Amyloidosis, which is an abnormal buildup of protein in different organs and body tissues
Low protein levels in the blood can indicate malnutrition, but eating high-protein foods does not necessarily raise blood protein levels.
What protein in the urine can mean
It is normal to have small amounts of protein in the urine. When protein levels rise briefly, this is often due to factors like exposure to intense cold or heat, high fever, vigorous exercise, or stress, and usually is not a cause for concern.
However, a persistent increase in urine protein can be a sign of underlying problems. According to the National Kidney Foundation, albuminuria, also called proteinuria, may happen when the kidney’s filters are damaged.