Complete Blood Count (CBC): What This Common Blood Test Measures and What Your Results Can Show

The complete blood count, or CBC, is one of the most frequently ordered blood tests. It measures the main types of cells in your blood: red blood cells, which carry oxygen throughout your body; white blood cells, which help fight infection; and platelets, which allow your blood to clot properly after an injury.

The Borrelia burgdorferi IgG+IgM antibody test is a blood test that detects your immune system's response to Borrelia burgdorferi, the bacterium transmitted through tick bites that causes Lyme disease. The test measures two types of antibodies: IgM (immunoglobulin M), which typically appear first during early infection, and IgG (immunoglobulin G), which develop later and remain in your system for longer.

Your doctor may order this test as part of a routine checkup, or to help find the cause of symptoms such as fatigue, weakness, fever, unexplained bruising, or unusual bleeding. It is also used to monitor ongoing conditions like anemia or infection, and to check how treatments such as chemotherapy are affecting your blood cells.

Your healthcare provider may order this test if you have symptoms of Lyme disease, especially if you have been exposed to areas where Lyme disease is common or remember a tick bite. Common symptoms include the characteristic bull's-eye rash (erythema migrans), fever, headache, fatigue, and muscle aches. Early detection and treatment are important for preventing more serious complications that can affect the joints, heart, and nervous system.

The test is performed with a simple blood draw. A health care professional will clean a spot on your arm, usually the inside of your elbow, wrap a band around your upper arm, and use a small needle to collect a blood sample into a tube. The process takes only a few minutes, and you may feel a quick pinch. A small bandage is placed on the site afterward, and you can return to your normal activities right away.

A healthcare professional will draw a small blood sample from a vein in your arm. The sample is then sent to a laboratory where it is tested for the presence of IgM and IgG antibodies against Borrelia burgdorferi. The test is typically performed using enzyme-linked immunosorbent assay (ELISA) as an initial screening, followed by Western blot testing if the initial result is positive or indeterminate.

Your results show whether your blood cell counts fall within normal ranges. A low red blood cell count may suggest anemia, while a high white blood cell count can point to infection or inflammation. Abnormal platelet levels may affect how your blood clots. Results outside the normal range do not always indicate a serious problem, so your doctor will review them together with your symptoms, medical history, and other tests before explaining what they mean for you.

Results can be negative, positive, or indeterminate. A negative result means no antibodies were detected, but this could occur if you were infected very recently and antibodies have not yet developed. A positive result indicates that antibodies were found, suggesting either current or past infection. Your healthcare provider will interpret the results in context of your symptoms, when you may have been exposed, and the timing of your test. Sometimes, testing is repeated after 2-4 weeks to see if antibody levels are rising, which helps confirm an active infection.