Testing
Diagnostic techniques for human infection are Indirect Immunofluorescent Assay (IFA), examination of Giemsa-stained blood smears and identification of Babesial DNA by Polymmerase Chain Reaction (PCR).

Babesia can be overlooked during microscopic examination of thin blood smears because parasitemia can be sparse early in the course of infection, infecting less than 1% of erythrocytes.