Serum Protein Electrophoresis (SPEP): How to Read Your Results and an M Spike

An SPEP report can look intimidating: a curve, a row of fractions and sometimes a line that says "monoclonal band detected." The test places a drop of serum in an electric field. Each protein travels at its own speed, so the proteins gather into bands that the lab measures and draws as peaks^[1][2]. This guide reads the whole report with you: each fraction, the common patterns, what an M spike means and which tests usually come next. If only one band is flagged, the dedicated pages go deeper, starting with our guide to gamma globulin results, the band where most spikes appear.

What does a serum protein electrophoresis report look like?

Most US labs report the total protein, five fractions in grams per deciliter (g/dL), a line for any monoclonal protein and a written interpretation. Some labs also give percentages or split beta into beta-1 and beta-2.

Fictitious example of a serum protein electrophoresis report (United States format)

Test	Result	Reference range	Flag
Total protein, serum	7.8 g/dL	6.5-8.1 g/dL
Albumin	3.90 g/dL	3.75-5.01 g/dL
Alpha-1 globulin	0.30 g/dL	0.19-0.46 g/dL
Alpha-2 globulin	0.85 g/dL	0.48-1.05 g/dL
Beta globulin	0.95 g/dL	0.48-1.10 g/dL
Gamma globulin	1.80 g/dL	0.62-1.51 g/dL	H
Monoclonal protein (M spike)	0.72 g/dL	None detected	A
Interpretation	Monoclonal band in the gamma region. Immunofixation: IgG kappa.

1. Total protein: the sum of all bands. It can be normal even when one band hides a problem, as here.
2. Albumin: the largest peak, made by the liver. Low albumin points to liver disease, protein loss through the kidneys or gut, poor nutrition or inflammation^[2].
3. Alpha-1 and alpha-2: carry acute-phase proteins that rise with inflammation^[2].
4. Beta: mostly transferrin (the iron carrier) and complement^[2].
5. Gamma, flagged H: the antibody band. Here it is high because it contains a narrow spike.
6. M spike 0.72 g/dL: the size of the monoclonal protein, the number your clinician will follow over time. A spike is never "normal," which is why it carries a flag even without a range.
7. Immunofixation IgG kappa: names the antibody type that makes the spike^[3]. Ranges come from one reference lab^[4]: always read yours against your own lab's ranges.

What does each protein fraction measure?

Each band is a family of proteins, not a single one. The table gives typical adult ranges from two US sources; ranges differ with the method (gel or capillary), so your lab's range is the one that counts.

Serum protein electrophoresis fractions, what they contain and typical adult reference ranges

Fraction	Main proteins	Range, reference lab (capillary)[4]	Range, MedlinePlus[1]	Full guide
Albumin	Albumin	3.75-5.01 g/dL	3.6-4.8 g/dL	Albumin blood test
Alpha-1	Alpha-1 antitrypsin, acid glycoprotein	0.19-0.46 g/dL	0.2-0.4 g/dL	Alpha-1 globulin
Alpha-2	Haptoglobin, ceruloplasmin, alpha-2 macroglobulin	0.48-1.05 g/dL	0.6-0.9 g/dL	Alpha-2 globulins
Beta (beta-1 and beta-2)	Transferrin, complement C3, lipoproteins	0.48-1.10 g/dL	0.6-1.1 g/dL	Beta-1 and beta-2 globulin
Gamma	Immunoglobulins (IgG, IgA, IgM)	0.62-1.51 g/dL	0.8-1.8 g/dL	Gamma globulins
Total protein	All of the above	Range on the report	6.5-8.1 g/dL	Total protein test

To convert g/dL to g/L, multiply by 10 (3.9 g/dL = 39 g/L). Labs outside the United States often report percentages of total protein instead.

How do you read the patterns on a protein electrophoresis?

Clinicians look at the shape of the curve and at which bands move together. The same rise in gamma globulin can be harmless or important depending on whether it is broad or narrow^[2].

Common serum protein electrophoresis patterns and what they usually suggest

Pattern	What changes	Frequent causes
Acute inflammation	Alpha-1 and alpha-2 up, albumin sometimes down	Infection, surgery, injury, flare of an inflammatory disease[2]
Chronic inflammation (polyclonal)	Broad, rounded rise of the whole gamma band	Long-lasting infection, autoimmune disease such as rheumatoid arthritis or lupus, chronic liver disease[1][2]
Liver disease	Low albumin with a broad gamma rise	Cirrhosis, chronic hepatitis[1][2]
Protein loss through the kidneys	Low albumin, high alpha-2	Nephrotic syndrome[1][2]
Monoclonal spike (M protein)	A narrow, sharp peak, usually in gamma, sometimes in beta	MGUS, multiple myeloma, Waldenström macroglobulinemia, amyloidosis[2]
Low gamma (hypogammaglobulinemia)	Flat, small gamma band	Medicines that target B cells, chronic lymphocytic leukemia, myeloma, protein loss; rarely an inherited immune deficiency[5]

Single-band changes are covered in each fraction guide. In short, a high beta band is often linked to iron deficiency or pregnancy, a low alpha-1 band can point to alpha-1 antitrypsin deficiency, and a low alpha-2 band to red blood cell breakdown (hemolysis)^[1][2]. Electrophoresis is a rough marker of inflammation; your clinician will usually rely on a CRP test or a sed rate for that.

What does an M spike on protein electrophoresis mean?

An M spike (monoclonal protein, or paraprotein) is a large amount of one identical antibody, made by a single family of plasma cells. It is a finding, not a diagnosis.

• Common MGUS (monoclonal gammopathy of undetermined significance): found in 3.2% of people aged 50 and older and 5.3% of those aged 70 and older in a large Minnesota study^[6]. In that study, the spike was smaller than 1.0 g/dL in 63.5% of cases. MGUS causes no symptoms and turns into a blood cancer in about 1% of people per year^[7].
• Possible Smoldering myeloma or Waldenström macroglobulinemia: a larger spike or more plasma cells in the bone marrow, still without organ damage; these need closer monitoring^[7].
• Rare Multiple myeloma or AL amyloidosis: diagnosed only with a bone marrow exam and signs of organ damage such as high calcium, kidney failure, anemia or bone lesions^[8]. Our multiple myeloma guide explains these criteria.

The size of the spike matters, but it is not the whole story. MGUS is defined by a spike below 3 g/dL, fewer than 10% plasma cells in the marrow and no organ damage^[8]. In myeloma the spike is usually larger than 3 g/dL, yet up to one fifth of people with myeloma have a spike below 1 g/dL^[2].

In a 34-year follow-up of 1,384 people with MGUS, the risk of progression was 10% at 10 years and 18% at 20 years. It was lowest (7% at 20 years for non-IgM MGUS) when the spike was below 1.5 g/dL and the kappa/lambda ratio was normal^[9].

What tests come after an abnormal protein electrophoresis?

SPEP is a screening picture. The next tests depend on the pattern:

• Serum immunofixation: identifies the type of monoclonal antibody (IgG, IgA or IgM, kappa or lambda) and can find a spike too small to see on the curve^[2][3].
• Serum kappa and lambda light chains: measures the light chains in the blood and their ratio; it helps when a myeloma makes only light chains and no visible spike^[3]. See our page on the kappa/lambda ratio.
• Quantitative immunoglobulins: IgG, IgA and IgM levels; in myeloma, one type is often high while the others are low^[3].
• Urine protein electrophoresis and immunofixation: often on a 24-hour urine collection, recommended when a plasma cell disorder is suspected^[2][3].
• Organ checks: complete blood count, calcium and creatinine, to look for anemia, high calcium and kidney damage^[8].
• Repeat SPEP: for low-risk MGUS (IgG type, spike below 1.5 g/dL, normal light chain ratio), a repeat test at 6 months, then every 2 to 3 years if stable, or sooner if symptoms appear^[7].

Closer follow-up, at 6 months and then every year, is advised when the spike is 1.5 g/dL or more, when it is IgA or IgM, or when the light chain ratio is abnormal^[7]. Signs of organ damage lead to a prompt hematology visit^[8].

How should you prepare for a serum protein electrophoresis?

It is an ordinary blood draw from a vein, collected in a serum tube (often gold or red top). Many labs need no special preparation, while others ask for up to 12 hours of fasting^[1][4]: follow the instructions you were given, as explained in our guide on fasting before a blood test. Tell your clinician about recent vaccines, infections and all medicines, including hormones, because they can shift some bands^[1][10]. Do not stop a medicine on your own.

Frequently asked questions

Is serum protein electrophoresis a cancer test?

No. It is a general picture of blood proteins that can show inflammation, liver or kidney disease and immune problems. It is used to look for monoclonal proteins, but most spikes found turn out to be MGUS, which is not cancer^[6][7].

Can a normal SPEP miss multiple myeloma?

Yes, sometimes. Some myelomas make only light chains, which may not form a visible spike; about 10% of people with myeloma show a low gamma band instead^[2]. That is why immunofixation and a light chain test are added when myeloma is suspected^[3].

Can an M spike go away?

An MGUS spike usually stays stable for years; the goal of follow-up is to check that it does not grow^[7]. Your clinician will tell you how often to repeat the test.

What is the difference between serum and urine protein electrophoresis?

Serum electrophoresis studies proteins in the blood. Urine electrophoresis looks for proteins that filter into the urine, such as light chains (Bence Jones protein), which can be missed in blood^[3][10].

Can dehydration change the result?

Yes. Dehydration concentrates the blood and can raise albumin and total protein; a recent vaccine or infection can raise antibodies in the gamma band^[10]. A borderline result is often simply repeated.

Related tests and guides

• Gamma globulinsThe antibody band, high or low, explained in depth.
• Kappa/lambda ratioThe light chain test that often follows an M spike.
• Multiple myelomaSymptoms, diagnosis criteria and treatment.
• Total proteinThe single number that often leads to an SPEP.
• HaptoglobinThe alpha-2 protein that falls with hemolysis.

References

1. MedlinePlus Medical Encyclopedia. Serum protein electrophoresis. medlineplus.gov (accessed November 2, 2026)
2. O'Connell TX, Horita TJ, Kasravi B. Understanding and interpreting serum protein electrophoresis. Am Fam Physician. 2005;71(1):105-112. aafp.org (PubMed 15663032, accessed November 2, 2026)
3. American Cancer Society. Tests to find multiple myeloma. cancer.org (accessed November 2, 2026)
4. ARUP Laboratories. Protein electrophoresis, serum (test 0050640): reference intervals, specimen and turnaround. aruplab.com (accessed November 2, 2026)
5. Patel SY, Carbone J, Jolles S. The expanding field of secondary antibody deficiency: causes, diagnosis, and management. Front Immunol. 2019;10:33. doi:10.3389/fimmu.2019.00033 (accessed November 2, 2026)
6. Kyle RA, Therneau TM, Rajkumar SV, et al. Prevalence of monoclonal gammopathy of undetermined significance. N Engl J Med. 2006;354(13):1362-1369. doi:10.1056/NEJMoa054494 (accessed November 2, 2026)
7. Kyle RA, Durie BGM, Rajkumar SV, et al. Monoclonal gammopathy of undetermined significance (MGUS) and smoldering (asymptomatic) multiple myeloma: IMWG consensus perspectives risk factors for progression and guidelines for monitoring and management. Leukemia. 2010;24(6):1121-1127. doi:10.1038/leu.2010.60 (accessed November 2, 2026)
8. Rajkumar SV, Dimopoulos MA, Palumbo A, et al. International Myeloma Working Group updated criteria for the diagnosis of multiple myeloma. Lancet Oncol. 2014;15(12):e538-e548. doi:10.1016/S1470-2045(14)70442-5 (accessed November 2, 2026)
9. Kyle RA, Larson DR, Therneau TM, et al. Long-term follow-up of monoclonal gammopathy of undetermined significance. N Engl J Med. 2018;378(3):241-249. doi:10.1056/NEJMoa1709974 (accessed November 2, 2026)
10. Testing.com. Protein electrophoresis and immunofixation electrophoresis. testing.com (accessed November 2, 2026)
11. Medicare.gov. Diagnostic laboratory tests. medicare.gov (accessed November 2, 2026)

This article is general health information. It does not replace a medical examination, diagnosis or treatment. An abnormal electrophoresis needs to be interpreted by your clinician with your symptoms and other results.