Hematocrit determination

This test measures the volume (amount) of red blood cells (RBC) compared to other components in blood. Test results are reported as a percentage or as a decimal fraction of whole blood. This test may be used to evaluate or manage diseases such as end-stage renal (kidney) disease, or heart failure.

Laboratory tests may be done for many reasons. Tests are performed for routine health screenings or if a disease or toxicity is suspected. Lab tests may be used to determine if a medical condition is improving or worsening. Lab tests may also be used to measure the success or failure of a medication or treatment plan. Lab tests may be ordered for professional or legal reasons. You may need this test if you have:

• Acute excessive bleeding
• Acute gastrointestinal hemorrhage
• Atrial myxoma
• Burn caused by heat
• Ehrlichiosis
• End-stage kidney disease
• Hantavirus pulmonary syndrome
• Heart failure
• Increased red blood cells
• Iron deficiency anemia
• Meckel's diverticulum
• Pancreatitis
• Pre-eclampsia
• Shock from blood loss
• Shock from heart not pumping blood

Venous or capillary blood:

Before having blood collected, tell the person drawing your blood if you are allergic to latex. Tell the healthcare worker if you have a medical condition or are using a medication or supplement that causes excessive bleeding. Also tell the healthcare worker if you have felt nauseated, lightheaded, or have fainted while having blood drawn in the past.

Avoid strenuous exercise before this test.

Umbilical cord blood:

Ask the healthcare worker for information about how to prepare for this test.

A sample of venous, capillary, or umbilical cord blood may be collected for this test.

Venous blood:

When a blood sample from a vein is needed, a vein in your arm is usually selected. A tourniquet (large rubber strap) may be secured above the vein. The skin over the vein will be cleaned, and a needle will be inserted. You will be asked to hold very still while your blood is collected. Blood will be collected into one or more tubes, and the tourniquet will be removed. When enough blood has been collected, the healthcare worker will take the needle out.

Capillary blood:

Common sites to collect a capillary blood sample are the fingertip and earlobe. Infants often have a capillary blood sample taken from the heel of the foot. Once the site is selected, the healthcare worker may heat the area with a warm compress to ensure adequate blood flow. The area will be cleaned with antiseptic. A small needle is used to make a cut in the skin surface, and the area may be squeezed gently to produce blood. The blood is collected in small collection device.

Umbilical cord blood:

A method called percutaneous umbilical cord blood sampling may be used to collect an umbilical cord blood sample. For this method, a needle is inserted through the pregnant mother's abdomen and into the umbilical cord. Ultrasound is used to help guide the needle. Samples of the unborn baby’s umbilical cord blood are drawn out for testing. When enough blood is collected, the needle is removed.

The amount of discomfort you feel will depend on many factors, including your sensitivity to pain. Communicate how you are feeling with the person doing the test. Inform the person doing the test if you feel that you cannot continue with the test.

Venous or capillary blood:

During a blood draw, you may feel mild discomfort at the location where the blood sample is being collected.

Umbilical cord blood:

There are several different ways that a cord blood sample may be collected. Depending on the procedure used to obtain the sample, the test may be uncomfortable. Ask the healthcare worker to explain how the test may feel.

Venous blood:

After a blood sample is collected from your vein, a bandage, cotton ball, or gauze may be placed on the area where the needle was inserted. You may be asked to apply pressure to the area. Avoid strenuous exercise immediately after your blood draw. Contact your healthcare worker if you feel pain or see redness, swelling, or discharge from the puncture site.

Capillary blood:

After capillary blood collection is complete, cotton will be placed over the site and held firmly until the bleeding has stopped. A bandage or cotton may be secured over the site.

Umbilical cord blood:

Depending on the procedure used to obtain a sample of cord blood, there may be special instructions for you to follow. Ask the healthcare worker for any special instructions following this procedure.

You have the right to help plan your care. To help with this plan, you must learn about your health condition and how it may be treated. You can then discuss treatment options with your caregivers. Work with them to decide what care may be used to treat you. You always have the right to refuse treatment.