Complete Blood Count (CBC) Test: What It Measures, Why Your Doctor Ordered It, and How to Understand Your Results

The complete blood count, commonly called a CBC, is a routine blood test that measures the different cells circulating in your blood, including red blood cells, white blood cells, and platelets, giving your doctor a broad picture of your overall health.

The Borrelia burgdorferi IgG+IgM antibody test is a blood test that looks for specific antibodies in your blood that your immune system produces when exposed to the bacteria Borrelia burgdorferi, which causes Lyme disease. The test detects two types of antibodies: IgM (immunoglobulin M), which are the first antibodies your body makes in response to an infection, and IgG (immunoglobulin G), which develop later and provide long-term immunity.

Your doctor may order a CBC as part of a routine checkup, to look into symptoms such as fatigue, weakness, fever, easy bruising, or unexplained bleeding, or to monitor an ongoing condition like anemia or infection and see how well your treatment is working.

Your healthcare provider may order this test if you have symptoms of Lyme disease, especially if you have been bitten by a tick or spent time in areas where Lyme disease is common. Common symptoms include a bull's-eye rash (erythema migrans), fever, headache, fatigue, and muscle or joint pain. Early detection and treatment are important for preventing complications of Lyme disease.

A healthcare professional will draw a small sample of blood from a vein in your arm, usually on the inside of your elbow, using a thin needle. The procedure takes only a few minutes, and you can generally return to your normal activities right away afterward.

A healthcare professional will draw a blood sample from a vein in your arm using a small needle. The blood is collected into a tube and sent to a laboratory for analysis. You may feel a brief stinging sensation when the needle is inserted or removed. The test usually involves a two-step process: an initial screening test (ELISA), followed by a confirmatory test (Western blot) if the screening result is positive or equivocal.

Your results show whether your blood cell counts fall within normal ranges. Values that are high or low can point to conditions such as anemia, infection, inflammation, or clotting problems, and your doctor will interpret them together with your symptoms and medical history.

Results are reported as positive, negative, or equivocal for IgG and IgM antibodies. A positive result indicates that antibodies were detected, suggesting a current or past Lyme disease infection. A negative result means no antibodies were detected, which could mean you do not have Lyme disease, or you were infected very recently and antibodies have not yet developed. It typically takes 1-2 weeks after infection for IgM antibodies to appear, and 4-6 weeks for IgG antibodies. An equivocal result means the test results are unclear and additional testing may be needed.