Blood test
The major test for myasthenia gravis is a blood test to search for a type of antibody (produced by the immune system) that prevents signals from being sent between the nerves and muscles. When these antibodies are present in large quantities, it means you have myasthenia gravis.
But not everyone with the disorder will have a high level of antibodies, especially if it’s only affecting the eye muscles (ocular myasthenia). The blood test may be repeated some other time if the result is normal but your symptoms continue or exacerbate.