What to know about the protein test and results
Having too many or too few proteins can lead to unexpected weight loss, fatigue, or inflammatory disease. The total protein test can help diagnose liver and kidney diseases, along with other conditions.
In this article, we discuss the total protein test, how to interpret the results, and what normal or abnormal protein levels might mean.
What is the total protein test?
The total protein test can help a doctor diagnose various conditions.
Proteins serve as building blocks for many organs, hormones, and enzymes. Proteins are essential for overall health, which is why routine health checkups often include a total protein test.
A total protein test measures the total number of proteins present in body fluid. The test examines protein in either urine or the liquid portion of the blood, which medial professionals call the serum.
A serum total protein test measures the amount of albumin and globulin present in the serum portion of the blood:
- Albumin protein accounts for half of the total protein found in blood plasma. It regulates oncotic pressure in the plasma to prevent water from leaking out of the blood vessels.
- Globulin proteins vary in size, weight, and function. They are grouped by how they migrate on electrophoresis and include α1, α2, β and γ fractions. They include carrier proteins, enzymes, complement, and immunoglobulins (also called antibodies).
A urine total protein test detects the amounts of protein present in the urine.
The kidneys filter albumin and other proteins from the blood so that the urine may contain small amounts of protein.
However, problems with the urinary tract, such as chronic kidney disease, can cause large amounts of protein to leak into the urine.
Normal protein levels in urine and blood
Laboratories may use slightly different total protein ranges, depending on the testing method and equipment they use.
The normal range for protein levels in blood serum is 6 to 8 grams per deciliter (g/dl). Of this, albumin makes up 3.5 to 5.0 g/dl, and the rest is total globulins. These ranges may vary between different laboratories.
Usually, a person's body eliminates less than 150 milligrams (mg) of total protein and less than 20 mg of albumin through the urine every 24 hours.
High or low serum or urine protein levels do not always signal a chronic medical condition. Everyday factors that can affect a person's protein levels include:
- intense exercise
- degree of hydration during the test
- taking hormonal birth control pills
- complications from surgery
Normal protein levels in pregnancy
Women who are pregnant can safely take either the serum or urine total protein tests.
When a person is pregnant, they may need to have their urine tested for any signs of proteinuria, which is excess protein in the urine.
When do I need a total protein test?
A doctor may recommend a total protein test if a person experiences loss of appetite.
A doctor may order a serum total protein test during a routine health checkup as part of a comprehensive metabolic panel (CMP).
Doctors may also use a total protein test to help diagnose a variety of diseases that affect protein levels.
People who have medical conditions that affect their gastrointestinal (GI) tract, liver, or kidneys may take total protein tests during follow-up visits to monitor their recovery during treatment.
A doctor might order a total protein test if a person has any of the following:
- unexpected weight loss
- loss of appetite
- edema or swelling due to excess tissue fluid
- difficulty urinating
- nausea or vomiting
- symptoms of nutritional deficiency
Interpreting the results
A doctor will look at the results of the serum total protein test along with other test results to help diagnose medical conditions. They will analyze the results in the context of a person's overall CMP.
If protein levels are not healthy, the doctor may recommend further tests.
What do high protein levels mean?
Consistently high serum total protein levels can indicate the following health conditions:
- inflammation from infections, such as HIV or viral hepatitis
- cancers, such as multiple myeloma
- chronic kidney disease
- liver disease
What do low protein levels mean?
Low serum total protein levels may suggest any of the following health conditions:
- malabsorption disorders, such as celiac disease or inflammatory bowel disease (IBD)
- liver disease
- kidney disease, such as nephrotic syndrome or glomerulonephritis
- congestive heart failure
Albumin to globulin ratio
Alongside the serum total protein level, a laboratory may calculate the albumin to globulin (A/G) ratio in the bloodstream. This is because some conditions affect the amounts of albumin or globulin in the blood.
A low A/G ratio may be due to an overproduction of globulin, underproduction of albumin, or loss of albumin, which may indicate the following:
- an autoimmune disease
- cirrhosis, involving inflammation and scarring of the liver
- multiple myeloma
- nephrotic syndrome kidney disease
A high A/G ratio may suggest:
A total protein test requires either a blood or urine sample.
A healthcare provider administers a total protein test in a clinic or other healthcare setting. Unless instructed otherwise, people do not need to make any special preparations before taking the test.
A serum total protein test involves drawing a sample of blood from a vein located in the arm.
A healthcare provider or phlebotomist will tie an elastic band around the upper arm to make the veins easier to find. After disinfecting the entry site, they will insert the needle into a vein. Blood from the vein will pass through the needle and into a collection tube.
Once the healthcare provider collects enough blood, they will remove the needle and the elastic band from the arm, apply pressure to the injection site, and cover the wound with a bandage.
A urine total protein test involves collecting a sample of urine. People can do this at home or in a healthcare setting.
A healthcare provider may ask that people collect urine at home over a 24-hour period.
Proteins play essential roles in supporting vital bodily functions, such as digestion, blood clotting, and energy production.
A healthcare provider may perform a total protein test during a routine health checkup. A total protein test measures the amount of protein present in the blood serum or urine.
A total protein test can detect normal or abnormal protein levels, which can help diagnose medical conditions, such as kidney and liver diseases.