Anti-Cardiolipin Antibodies
Also known as: aCL
What Does Anti-Cardiolipin Antibodies Measure?
Anti-Cardiolipin Antibodies (aCL) are a type of autoantibody measured in the blood that target cardiolipin, a phospholipid found in the inner membrane of mitochondria and on the surface of platelets and endothelial cells. The test measures the level of these antibodies in three immunoglobulin classes — IgG, IgM, and IgA — using a unit called GPL, MPL, or APL units respectively. Elevated levels indicate that the immune system is mistakenly attacking the body's own phospholipid structures.
Why Does Anti-Cardiolipin Antibodies Matter?
Anti-cardiolipin antibodies are clinically significant because they are strongly associated with Antiphospholipid Syndrome (APS), an autoimmune condition that dramatically increases the risk of blood clots (thrombosis) in both arteries and veins, as well as pregnancy complications such as recurrent miscarriage, stillbirth, and preeclampsia. Persistently elevated aCL levels are one of the laboratory criteria used to diagnose APS. They are also associated with systemic lupus erythematosus (SLE) and other autoimmune diseases, making this test a critical tool in evaluating unexplained clotting events or recurrent pregnancy loss.
Normal Ranges
Males
IgG: <20 GPL units/mL; IgM: <20 MPL units/mL; IgA: <20 APL units/mL
Females
IgG: <20 GPL units/mL; IgM: <20 MPL units/mL; IgA: <20 APL units/mL
Children
IgG: <20 GPL units/mL; IgM: <20 MPL units/mL; reference ranges may vary by lab
Causes of High Levels
- Antiphospholipid Syndrome (APS) — the primary cause of persistently elevated aCL antibodies
- Systemic Lupus Erythematosus (SLE) — up to 50% of lupus patients may have elevated aCL
- Infectious diseases — syphilis, HIV, hepatitis C, and Lyme disease can transiently elevate aCL
- Certain medications — hydralazine, procainamide, phenothiazines, and some antibiotics
- Other autoimmune diseases — rheumatoid arthritis, Sjögren's syndrome, and inflammatory bowel disease
- Malignancies — some cancers, particularly lymphomas and solid tumors, can induce aCL production
Causes of Low Levels
- Absence of autoimmune disease — low or undetectable levels are normal in healthy individuals
- Successful immunosuppressive therapy — treatment with corticosteroids or other immunosuppressants can reduce antibody levels
How to Improve Your Anti-Cardiolipin Antibodies
Diet
- Follow an anti-inflammatory Mediterranean-style diet rich in fruits, vegetables, whole grains, and olive oil to reduce systemic inflammation
- Increase omega-3 fatty acid intake through fatty fish (salmon, mackerel, sardines) at least 2-3 times per week to help modulate immune activity
- Reduce consumption of processed foods, refined sugars, and trans fats that promote inflammation and immune dysregulation
- Ensure adequate vitamin D intake through fortified foods, fatty fish, and egg yolks, as deficiency is linked to autoimmune activity
- Limit alcohol consumption, which can exacerbate autoimmune inflammation and interact with anticoagulant therapy
Supplements
- Vitamin D3: 1,000–4,000 IU/day (under physician supervision) to support immune regulation — deficiency is common in autoimmune conditions
- Omega-3 fish oil: 2–4 g/day of EPA+DHA to help modulate inflammatory pathways (check with physician if on anticoagulants)
- Hydroxychloroquine (prescription only): commonly prescribed for APS/lupus patients and has been shown to reduce aCL levels
- Magnesium: 200–400 mg/day to support vascular health and reduce inflammation associated with autoimmune conditions
Related Biomarkers
Frequently Asked Questions
What does it mean if my anti-cardiolipin antibody test is positive?
A positive aCL test means your blood contains antibodies that target cardiolipin, a natural phospholipid in your body. A single positive result does not automatically mean you have Antiphospholipid Syndrome (APS). To diagnose APS, the test must be positive on two or more occasions at least 12 weeks apart, and you must also have a clinical history of blood clots or pregnancy complications. A doctor may order additional tests such as lupus anticoagulant and anti-beta-2 glycoprotein I antibodies to complete the evaluation.
Can anti-cardiolipin antibodies cause miscarriage?
Yes, elevated aCL antibodies are one of the leading autoimmune causes of recurrent pregnancy loss. They can interfere with the normal development of the placenta by promoting clot formation in placental blood vessels, which reduces blood flow and nutrients to the fetus. Women with persistently elevated aCL and a history of recurrent miscarriage are often diagnosed with obstetric APS and treated with low-dose aspirin and low molecular weight heparin (LMWH) during pregnancy to improve outcomes.
Do I need to be on blood thinners if my aCL is elevated?
Not necessarily. The decision to start anticoagulation (blood thinners) depends on several factors: whether you have had a previous blood clot or stroke, whether aCL levels are persistently elevated, and whether you have other risk factors for thrombosis. People with elevated aCL but no prior clot may be monitored carefully or given low-dose aspirin. Those with a confirmed clot history and APS diagnosis typically require long-term anticoagulation with warfarin or heparin. Your physician will make this decision based on your full clinical picture.