Immunoglobulin M antibodies (IgM) are our first-line defense against a broad range of infections. They are often measured to help diagnose different conditions, such as infections, immunodeficiency, autoimmune disease, and certain types of cancer. Keep reading to learn more about high and low IgM levels and the factors that may affect them.
Antibodies are large proteins of the immune system that neutralize intruders, such as bacteria, viruses, fungi, and parasites. There are five main types of antibodies: IgA, IgD, IgE, IgG, and IgM.
IgM (Immunoglobulin M) are the largest antibodies. They are the first-line defense of our immune system. They provide general but short-term protection against new infections. IgM levels decline as the body starts producing more IgG antibodies, which are responsible for long-term protection against pathogens [1, 2].
Apart from “immune” IgM antibodies, which are produced in response to infections, we also have “natural” IgM antibodies that circulate in the blood without exposure to any intruders (antigens) [1, 3]. These are responsible for removing damaged and pre-cancerous cells, thereby also decreasing inflammation and protecting us from autoimmunity [4, 5, 6].
The normal range for IgM in the blood is around 40 – 250 mg/dL (milligrams per deciliter). However, ranges can differ between labs due to differences in equipment, techniques, and chemicals used.
Women normally have higher IgM levels than men .
Doctors will often order IgM, IgA, and IgG, and IgE together to get more accurate information about the immune system response.
Antibodies are measured to help diagnose different conditions, such as infections, immunodeficiency, autoimmune disease, and certain types of cancer.
However, just because your levels are high or low does not mean you have any of these conditions. Your doctor will interpret your result, taking into account your medical history, symptoms, and other test results.
Having too few immunoglobulins may make people more susceptible to infections. Having too many, on the other hand, may signal an overactive immune system.
Low levels of IgM may mean your immune system is not working optimally. Because this antibody helps provide protection against bacteria and viruses, having low IgM levels has been associated with a higher risk of recurring infections .
Causes listed below are commonly associated with low IgM levels. Work with your doctor or other health care professional to get an accurate diagnosis.
The following lifestyle choices may decrease IgM levels:
Further, these diseases and disorders are associated with lower IgM levels:
- Some autoimmune and inflammatory diseases, such as:
- Diabetes [18, 19]
- Selective immunoglobulin M deficiency, a rare and sometimes hereditary disorder [13, 20]
- Wiskott-Aldrich syndrome, a rare immune deficiency disorder 
- Lymphoid nodular hyperplasia 
- Leukemia 
Some people with low IgM levels may not show any symptoms at all. Other people will suffer from recurring infections .
The most important thing is to work with your doctor to find out what’s causing your low IgM and to treat any underlying conditions. IgM is just a marker. You should talk to your doctor about the best approaches to strengthen your immune response and improve your overall health.
You may try the additional strategies listed here if you and your doctor determine that they could be appropriate. None of these strategies should ever be done in place of what your doctor recommends or prescribes.
Refrain from smoking and drinking alcohol. In a study of over 1.7k people, alcohol or smoking had little effect on IgM in isolation. However, combined with smoking, even low levels of alcohol consumption significantly decreased IgM in the blood .
Limited studies suggest that the following supplements may help increase IgM levels:
- Lycopene (in human and animal studies) [24, 25]
- Ginseng (in animal studies) [26, 27, 28]
- Astragalus (in animal studies) [29, 30]
However, proper clinical trials are lacking to support their use.
There are two types of IgM antibodies: natural and immune [1, 3]. The body produces immune IgM antibodies in response to intruders (antigens). That is why IgM levels tend to increase during the initial phase of infections. IgM levels eventually decline as the body starts producing more IgG antibodies .
Doctors often use specific IgM antibodies to diagnose acute infections, such as hepatitis, CMV, EBV, HIV, measles, rubella, and mumps. However, the tests for specific IgM antibodies can be falsely positive – they can be elevated even when there is no disease present. That’s why it is prudent to follow up this test with one or several more reliable tests .
Causes listed below are commonly associated with high IgM levels. Work with your doctor or other health care professional for an accurate diagnosis.
IgM levels can increase due to:
- Infections [32, 33, 31, 34]. Viral and bacterial infections are the most common causes of high IgM levels.
- Some autoimmune disorders, including:
- Kidney damage. In kidney damage proteins such as albumin and IgG are lost through urine (nephrotic syndrome), but IgM in the blood conversely increases [39, 40].
- Hyper-immunoglobulin M syndromes, a group of genetic immunodeficiency disorders with high IgM and low levels of other immunoglobulins [41, 42]
- Louis-Bar syndrome (ataxia-telangiectasia), a rare genetic neurodegenerative disease 
- Cancers, such as multiple myeloma and Waldenstrom’s macroglobulinemia (a type of non-Hodgkin’s lymphoma) [44, 45, 46, 47]
The following conditions have been associated with high IgM levels in some studies. However, the below-outlined studies deal only with associations. A cause-and-effect relationship has not been established.
Metabolic syndrome is a condition characterized by three or more of the following conditions: fat around the stomach, high blood pressure, high blood sugar levels, high triglyceride levels, and low HDL-C levels.
In a study of over 9.3k people, higher IgM levels (above 110 mg/dL for men and 150 mg/dL for women) were associated with a higher incidence of metabolic syndrome (elevated triglycerides and lower HDL-C in particular) .
In a study of over 4.2k US army personnel, higher IgM levels were associated with higher all-cause mortality . Since high IgM levels are often a consequence of infectious and autoimmune diseases, these may have increased mortality in this study, though a clear cause and effect has not been established.
To decrease IgM levels, you need to work on resolving the underlying health issue with a healthcare professional.