Complete Blood Count (CBC): What It Measures and Why Your Doctor May Order It

What is this test? A complete blood count (CBC) is a common blood test that measures the different cells in your blood, including red blood cells, white blood cells, and platelets. Doctors order it to check your overall health and to help detect conditions such as anemia, infections, and other blood disorders.

Beta frequency relative power on EEG is a brain wave test that measures the proportion of your brain's electrical activity that falls in the beta frequency range (13-30 Hz). Beta waves are fast brain waves associated with wakefulness, alertness, active thinking, and concentration. This test uses electroencephalography (EEG) technology to record your brain's electrical signals through electrodes placed on your scalp.

How is the test performed? A trained health care professional will clean the skin on your arm, wrap an elastic band around your upper arm, and draw a small sample of blood from a vein, usually in your elbow or the back of your hand. The sample is then sent to a laboratory, where it is analyzed and the results are reported to your doctor.

During the test, a technician will place small electrodes on your scalp using a special cap or adhesive. These electrodes detect the electrical activity of your brain and transmit it to a computer for analysis. You will typically be asked to relax with your eyes closed during the recording. The procedure is painless, non-invasive, and usually takes 30-60 minutes. Sometimes you may be asked to perform certain tasks like deep breathing or looking at flashing lights to see how your brain responds.

How to prepare for the test? In most cases, no special preparation is needed, and you can eat and drink normally before the test. Be sure to tell your provider about any medicines, vitamins, or supplements you take, since some can affect the results. If your blood draw is combined with other tests that require fasting, your care team will give you specific instructions.

Wash your hair thoroughly the night before or the morning of the test. Avoid using hair products like gels, mousses, or oils as they can interfere with electrode contact. Continue taking your regular medications unless your doctor instructs otherwise. Get adequate sleep the night before as fatigue can affect results. Bring a list of your current medications to the appointment.