This test checks the amount of certain antibodies called immunoglobulins in your body.
Some conditions cause your body to make too many or too few immunoglobulins.
Types of Immunoglobulin
Your body makes a few different types of immunoglobulin antibodies, including these:
Immunoglobulin A: IgA antibodies are found in the mucous membranes of the lungs, sinuses, stomach, and intestines. They're also in fluids these membranes produce, like saliva and tears, as well as in the blood.
Immunoglobulin G: IgG is the most common type of antibody in your blood and other body fluids. These antibodies protect you against infection by "remembering" which germs you've been exposed to before.
If those germs come back, your immune system knows to attack them. Your doctor can test for IgG to figure out whether you've been infected by certain kinds of bacteria or virus.
Immunoglobulin M: Your body makes IgM antibodies when you are first infected with new bacteria or other germs.
They are your body's first line of defense against infections. When your body senses an invader, your IgM level will rise for a short time. It will then begin to drop as your IgG level kicks in and increases to protect you long-term.
Immunoglobulin E: Your body makes IgE antibodies when it overreacts to substances that aren't harmful, such as pollen or pet dander. Your doctor will likely measure your IgE levels if you have a blood test to check for allergies.
Why You Might Need This Test
They may also order the test if you have:
How the Test is Done
Doctors often measure IgA, IgG, and IgM together to get a snapshot of your immune function. A lab tech will usually take a sample of your blood by inserting a needle into a vein in your arm. The blood collects into a tube or vial.
Another way to do this test is with a sample of what’s called cerebrospinal fluid (CSF).
CSF surrounds your brain and spinal cord. The doctor will take a sample of this fluid with a lumbar puncture (often called a “spinal tap”).
For this, you go to an outpatient facility or a hospital. A technician will give you a shot in your back to help numb any pain.
You will likely lie on your side with your knees pulled up to your chest, or you sit on a table. The technician inserts a hollow needle between two vertebrae in your lower spine and removes a small amount of fluid so it can be tested.
What Do My Results Mean?
The sample will be sent to a lab for testing. This might take a few days.
Depending on your results, the doctor might need to do other tests, such as a:
If your immunoglobulin level is high, it might be caused by:
- Chronic infections
- An autoimmune disorder that makes your immune system overreact, such as rheumatoid arthritis, lupus, or celiac disease
- Liver disease
- Inflammatory bowel disease
- Cancer, such as multiple myeloma, lymphoma, or leukemia
Low levels of immunoglobulins mean your immune system isn't working as well as it should. This can be caused by:
- Medicines that weaken your immune system, such as steroids
- Diabetes complications
- Kidney disease or kidney failure
- A weakened immune system that you were born with or developed (as with HIV/AIDS)
Just because your immunoglobulin level is high or low doesn't mean you have one of these conditions.
Each person's test can differ based on the method the lab uses to check the results. Talk to your doctor about your test results, and find out what you should do next.