Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.
Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.
The blood sample is sent to a lab. The test measures how fast red blood cells called erythrocytes fall to the bottom of a tall, thin tube.
There are no special preparations needed.
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
This test can be used to monitor inflammatory or cancerous diseases. It is a screening test, which means it cannot be used to diagnose a specific disorder.
However, it is useful in detecting and monitoring tuberculosis, tissue death, certain forms of arthritis, autoimmune disorders, and inflammatory diseases that cause vague symptoms.
Adults (Westergren method):
- Men under 50 years old: less than 15 mm/hr
- Men over 50 years old: less than 20 mm/hr
- Women under 50 years old: less than 20 mm/hr
- Women over 50 years old: less than 30 mm/hr
Children (Westergren method):
- Newborn: 0 to 2 mm/hr
- Neonatal to puberty: 3 to 13 mm/hr
Note: mm/hr. = millimeters per hour
An increased ESR rate may be due to:
Very high ESR levels occur with:
Lower-than-normal levels occur with:
Additional conditions that may affect test results:
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)