What blood tests are used to diagnose myasthenia gravis?

Reviewed by Yoshinori Abe, MD

Internal Medicine

Blood tests for myasthenia gravis detect specific autoantibodies—most commonly anti-acetylcholine receptor (AChR), anti-MuSK, and anti-LRP4 antibodies—that mistakenly attack proteins at the neuromuscular junction, disrupting communication between nerves and muscles. Identifying these antibodies helps confirm the diagnosis and guide treatment.

If you're experiencing muscle weakness, drooping eyelids, or unexplained fatigue, don't wait to get answers. A free, instant, online symptom check can help you understand what may be causing your symptoms, assess the likelihood of conditions like myasthenia gravis, and give you clear guidance on the next steps to take with your doctor—so you can move forward with confidence.

Reviewed for medical accuracy: 07/14/2026

Important Next Steps

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Explanation

To diagnose myasthenia gravis, doctors often use blood tests to find certain antibodies. These antibodies can attack parts of the muscles and nerves, making it hard for the body to move properly. If you're experiencing unexplained muscle weakness or fatigue, you can start by using a free AI symptom checker to help identify potential causes before seeing a healthcare provider.

Main Tests:

Acetylcholine Receptor Antibodies (AChR): This is the most common test. It checks for antibodies that attack the acetylcholine receptors, which are important for muscle movement.
Muscle-Specific Kinase (MuSK) Antibodies: If the AChR test is negative, doctors might look for MuSK antibodies. These are found in some people with myasthenia gravis, especially when AChR antibodies are not present.

Why These Tests Matter:

Identifying these antibodies helps doctors confirm if someone has myasthenia gravis.
Knowing which antibodies are present can guide treatment decisions.

These tests are important because they help doctors figure out if someone has myasthenia gravis and how to best treat it. Each test looks for different antibodies, which can give clues about the condition.

(References)

Zisimopoulou P, Brenner T, Trakas N, & Tzartos SJ. (2013). Serological diagnostics in myasthenia gravis based on .... Autoimmunity reviews, 23537507.
Mousavi A, Kumar P, & Frykman H. (2024). The changing landscape of autoantibody testing in .... Clinical biochemistry, 39357636.
Leite MI, Waters P, & Vincent A. (2010). Diagnostic use of autoantibodies in myasthenia gravis. Autoimmunity, 20380582.

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