Anticardiolipin IgM

Anticardiolipin IgM is a blood test that measures one type of antibody your immune system can make against cardiolipin, a phospholipid found in cell membranes. These antibodies are part of a group called antiphospholipid antibodies.

Doctors often order this test together with anticardiolipin IgG and anti–beta-2 glycoprotein I antibodies to look for an autoimmune condition known as antiphospholipid syndrome. The result helps show whether your immune system is producing IgM antibodies that may be relevant to clotting or certain pregnancy complications.

Finding anticardiolipin IgM can help explain why someone has had unexplained blood clots in veins or arteries, transient neurologic symptoms, pregnancy loss, preeclampsia, or low platelets. It is also checked when you have other autoimmune diseases, such as lupus, because the risk of clots can be higher in those settings.

A positive result does not automatically mean you have a disease. Some people have a temporary positive after an infection or other stress. Your clinician looks at the pattern of antiphospholipid antibodies, your history, and whether results remain present over time to decide on monitoring or treatment.

Your result is interpreted alongside other antiphospholipid tests and your medical history. A negative result makes antiphospholipid syndrome less likely but does not rule it out, especially if related symptoms or events have occurred. A low positive can be nonspecific and may be seen with infections or other illnesses.

If positive, your clinician may repeat testing after a period of time to confirm persistence and may add related tests. Management focuses on your personal risk of clotting or pregnancy complications, not just a single laboratory value. If results are positive and you have risk factors, your care team may discuss steps such as avoiding smoking, managing blood pressure and cholesterol, reviewing contraceptive options, and planning specialized care if you are pregnant or planning pregnancy.