Serum protein electrophoresis (SPEP) is a blood test that sorts proteins by size, shape and electrical charge. It measures protein levels and separates them into different groups. The results help providers detect conditions like infections, liver or kidney disease and autoimmune disorders.

What Is Protein Electrophoresis?

Protein electrophoresis is a test that separates and measures proteins. This is often performed on a sample of your blood (serum protein electrophoresis or SPEP). Proteins are important parts of your blood that help your body work. The test uses a blood sample and electrical current to group proteins based on their size, shape and electrical charge. Then, healthcare providers look at how much protein is in each group. These results can help find health problems that affect protein levels.

Your healthcare provider may order a serum protein electrophoresis test if you have:

  • Symptoms of a disease that causes abnormal protein levels
  • Irregular results from another blood test

Providers can also use your pee for protein electrophoresis (urine protein electrophoresis or UPEP).

Protein electrophoresis can help detect or diagnose conditions like:

  • Autoimmune diseases
  • Inflammation and infection
  • Kidney disease
  • Liver disease
  • Malnutrition
  • Monoclonal gammopathy of undetermined significance (MGUS)
  • Multiple myeloma

How does the test work?

Serum protein electrophoresis uses a blood sample and an electrical current to measure protein levels. Your blood has many different types of proteins. The two main proteins are called albumin and immunoglobulin. Each plays a unique role in helping your body work. If your levels are too high or too low, it can point to certain health problems.

Here’s how the test works:

  1. A healthcare provider collects a sample of blood from a vein in your arm.
  2. They place a small amount of your blood on a gel or in a special tube called a capillary.
  3. They apply electrical current to the sample.
  4. The proteins in your blood move through the gel or tube. How quickly they move and how they move are based on the type of protein it is.
  5. Your provider looks at the pattern the test creates. It should show the amounts and types of proteins in your blood and if they’re normal.

You don’t need to do anything to prepare for the test.

What are the risks of protein electrophoresis?

There’s little risk to the test. It’s very safe and only involves giving a sample of blood. You may have bruising in your arm where the blood was taken.

What type of results do you get?

You should receive your test results within a few days.

The test gives a result that shows the amount and patterns of different proteins in your blood. It may consist of two parts: a pattern (or graph) and then a measurement (or amount).

  • The graph will show abnormal highs and lows within each type of protein. These patterns form certain shapes that will stand out to your provider.
  • The measurement shows amounts (or ranges) of each with a number. It will show if a certain protein is higher or lower than average or normal.

Test results are just a starting point. Your healthcare provider typically needs additional tests to narrow down the cause or diagnose a condition.

What does an abnormal result mean?

Abnormal results on a protein electrophoresis test may point to a health condition. High levels in certain protein groups could mean inflammation, cancer or immune system disorders. Low levels could mean malnutrition, kidney disease or liver disease.

Your healthcare provider will review your results and let you know what comes next. Sometimes, your provider will order additional blood tests, urine tests or imaging tests to get closer to a diagnosis.

  • Chabrun F, Dieu X, Ferre M, et al. Achieving Expert-Level Interpretation of Serum Protein Electrophoresis through Deep Learning Driven by Human Reasoning (https://pubmed.ncbi.nlm.nih.gov/34491313/)Clin Chem. 2021 Oct;67(10):1406-1414. Accessed 12/16/2025.
  • Lee AY, Cassar PM, Johnston AM, et al. Clinical use and interpretation of serum protein electrophoresis and adjunct assays (https://pubmed.ncbi.nlm.nih.gov/28165779/)Br J Hosp Med (Lond). 2017 Feb;78(2):C18-C20. Accessed 12/16/2025.
  • Singh G. Serum and Urine Protein Electrophoresis and Serum-Free Light Chain Assays in the Diagnosis and Monitoring of Monoclonal Gammopathies (https://pubmed.ncbi.nlm.nih.gov/33150391/)J Appl Lab Med. 2020 Nov;5(6):1358-1371. Accessed 12/16/2025.
  • Srinivas PR. Introduction to Protein Electrophoresis (https://pubmed.ncbi.nlm.nih.gov/30426403/)Methods Mol Biol. 2019 Nov;1855:23-29. Accessed 12/16/2025.
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