Babesia microti Ab

What is Babesia microti Ab?

Measures antibodies made in response to Babesia microti, a tick-borne parasite that infects red blood cells and causes babesiosis.

This test detects antibodies against Babesia microti, a microscopic parasite spread mainly by blacklegged ticks that invades red blood cells. It relates to the immune system and to red blood cell health, since babesiosis can be associated with hemolysis (breakdown of red blood cells) in some cases. Clinicians commonly order it after known or suspected tick exposure, particularly when unexplained fever or anemia-type symptoms are present, or as part of a broader tick-borne disease panel alongside Lyme and Anaplasma testing. Antibody results are interpreted together with symptoms, blood smear findings when available, and exposure history rather than as a stand-alone answer.

Tests often checked alongside this

• Borrelia burgdorferi Ab (Lyme ELISA) — frequently co-tested due to shared tick exposure
• Anaplasma phagocytophilum Ab — another common tick-borne co-infection
• Complete Blood Count (CBC) — can reveal anemia patterns associated with babesiosis
• Peripheral blood smear — a complementary way parasites may be directly visualized

How this can show up in how you look and feel

• May be associated with fever, chills, or sweats following tick exposure
• May be associated with fatigue or muscle aches
• May be associated with signs of anemia, such as unusual paleness or breathlessness with exertion

What can affect this marker

• Timing of exposure relative to testing
• Immune status, including conditions or medications that affect immune response
• Prior tick-borne exposure history
• Concurrent infection
• Lab-to-lab variability in assay methods

What to track over time

• Whether antibody levels or blood smear findings change over time
• How results align with symptom onset and tick exposure history
• Whether follow-up blood counts are useful to monitor for anemia
• Repeat testing may be considered if initial testing was done very early in illness

What to ask your doctor

• Does this result suggest current or past exposure to this parasite?
• Should a blood smear or additional tick-borne panel be considered?
• Could my symptoms have another explanation?
• Is monitoring of my blood counts recommended?

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