Diagnosis
MGUS is usually found with blood tests done for other conditions or for regular checkups. When M proteins are found, you have more tests so your care team can better understand the condition and see whether there are signs of cancer or other organ damage. These tests include:
- Blood tests. Lab tests of blood samples tell your healthcare team more about the M proteins in your body and can show signs of organ damage.
- Serum protein electrophoresis (SPEP). SPEP looks for and measures M proteins. If an M protein is present, it may appear as an M spike. An M spike does not by itself mean that you have cancer.
- Immunofixation. This identifies the type of M protein, such as IgG kappa. It also helps tell the difference between a monoclonal protein and a polyclonal pattern. A polyclonal pattern means several types of antibodies are increased. This can happen with inflammation or infection and is different from the monoclonal protein found in MGUS.
- A serum free light chain test measures kappa and lambda light chains.
- Urine tests. Urine samples taken over 24 hours can help show M proteins and signs of kidney damage.
- Imaging tests. You may have imaging tests of the whole body to rule out damage to the bones or changes in the bone marrow.
- Bone marrow test. A hollow needle removes a piece of bone marrow from the back of one of the hip bones for study. This test usually is done only for those at risk of more-serious disease.
- Bone density test. You may have an X-ray test to measure the density of bone and look for signs of osteoporosis.
MGUS versus smoldering multiple myeloma
Test results also help your healthcare team confirm that you have MGUS rather than smoldering multiple myeloma (SMM) or active multiple myeloma.
SMM has more altered plasma cells in the bone marrow or more monoclonal protein than MGUS, but it does not cause the organ damage or other features of active multiple myeloma.
More Information
Treatment
MGUS doesn't require treatment. Your care team schedules regular checkups to repeat blood and urine tests to look for any rise in M proteins. You may have more tests if a change in M proteins suggests a higher risk of cancer or other diseases.
Watchful waiting
You'll likely have a first follow-up exam about six months after being diagnosed with MGUS. Your healthcare team decides how often to repeat exams depending on the risk of MGUS leading to cancer or other diseases.
Talk with your healthcare professional if you have new symptoms. Symptoms to watch for include:
- Bone pain.
- Tiredness or weakness.
- Weight loss without trying.
- Fever with no known cause.
- Frequent infections.
- Tingling or numbness in legs or arms.
- Easy bruising or bleeding.
- Trouble breathing.
- Confusion or trouble thinking.
Medicines
If you get osteoporosis, your care team may prescribe a medicine called a bisphosphonate to slow the loss of bone tissue. Examples include alendronate (Binosto, Fosamax), risedronate (Actonel, Atelvia), zoledronic acid (Reclast, Zometa) and ibandronate.
Prognosis
Most people with MGUS do not get a blood cancer.
Your outlook depends in part on the type and amount of M protein and your serum free light chain test results. Studies report different long-term outcomes, so a single life expectancy number does not apply to everyone with MGUS.
Can MGUS go away on its own?
Sometimes the M protein associated with MGUS becomes undetectable, but this is not common. In a long-term study, the M protein became undetectable without a known cause in about 2% of people with MGUS. This was more common when the M protein level was very low at diagnosis.
Preparing for your appointment
Your healthcare professional may refer you to a doctor who specializes in blood conditions, called a hematologist.
Here's information to help you get ready for your appointment.
What you can do
Ask a family member or friend to go with you. Someone who's with you can help you remember the information you get.
Make a list of:
- Your symptoms and when they began. Include symptoms that don't seem linked to the reason you made the appointment.
- Key information, including other illnesses you or people in your family have had.
- All medicines, vitamins and supplements you take, including the doses and the reasons for taking them.
Questions to ask your doctor
For MGUS, basic questions to ask your health professional include:
- What tests do I need?
- Do I need to do something to get ready for tests?
- How often do I need to come back?
- Should I start treatment or change my lifestyle?
- I have other health conditions. How can I best manage them together?
Be sure to ask all the questions you have.
What to expect from your doctor
Your healthcare professional is likely to ask you questions, including:
- Do your hands or feet tingle or feel numb?
- Have you had broken bones?
- Have you had a diagnosis of osteoporosis?
- Has someone in your family had MGUS or cancer of the blood?
- Have you ever had a blood clot?
Sept. 16, 2026