Complete Blood Count (CBC) Test: What to Expect

A complete blood count (CBC) is a common blood test that measures the cells circulating in your blood, including red blood cells, white blood cells, and platelets. Doctors order it to evaluate your overall health and to screen for or monitor many conditions, such as anemia, infections, and bleeding or clotting disorders.

The Borrelia burgdorferi antibody test is a blood test that looks for antibodies your immune system has produced in response to the bacteria that cause Lyme disease. Lyme disease is an infection transmitted through the bite of infected black-legged ticks (Ixodes scapularis). The test may be performed on serum (blood) or cerebrospinal fluid (CSF) to help diagnose Lyme disease, particularly when it affects the nervous system.

The test works by analyzing a small blood sample in a laboratory. An automated analyzer counts and measures each type of blood cell and reports values such as hemoglobin, hematocrit, and the white blood cell differential. Your doctor then compares these numbers with standard reference ranges to see whether any results are unusually high or low and what that may suggest about your health.

When your body is infected with Borrelia burgdorferi, your immune system produces specific antibodies. This test detects these antibodies using specialized laboratory techniques. The test typically uses an enzyme immunoassay (EIA) as an initial screening, followed by Western blot testing for confirmation—a process known as two-tiered testing.

During the test, a healthcare professional will wrap an elastic band around your upper arm, clean the skin at the draw site, usually the inside of your elbow, and insert a small needle into a vein to collect blood into one or more tubes. The process typically takes less than five minutes. You may feel a brief pinch or sting, and a cotton pad and bandage will be applied afterward.

A healthcare professional will draw a blood sample from a vein in your arm. For CSF testing, a lumbar puncture (spinal tap) is performed to collect fluid from around your spinal cord. The sample is then sent to a laboratory for analysis. The entire process usually takes a few days to a week for results.

Preparation is usually simple. You can normally eat and drink as usual and should keep taking your regular medications unless your doctor gives you different instructions. Wear a shirt with short or loose sleeves so your arm is easy to access, and drink plenty of water beforehand, since good hydration makes your veins easier to find. Let your provider know if you take blood thinners, have bleeding problems, or have ever felt faint during a blood draw.

No special preparation is typically needed for a blood test. If CSF collection is required, your doctor will provide specific instructions. Inform your healthcare provider about any recent infections, tick exposures, or symptoms you may be experiencing, as this information helps interpret the results.