Sedimentation rate (sed rate) test

The sedimentation rate (sed rate) test is a blood test. It measures how quickly red blood cells settle in a test tube. When there's inflammation in the body, the red blood cells stick together and fall more quickly than normal to the bottom of the tube.

A sed rate test is done to:

• Find out if inflammation is present.
• Check on the progress of a disease.
• See how well a treatment is working.

The health professional drawing blood will:

• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
• Clean the needle site with alcohol.
• Put the needle into the vein. More than one needle stick may be needed.
• Attach a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Apply a gauze pad or cotton ball over the needle site as the needle is removed.
• Apply pressure to the site and then a bandage.

In general, you won't need to prepare before your child has this test. Your doctor may give you some specific instructions.

• There are many possible causes of a high sed rate. For this reason, the test is done with other tests to confirm a diagnosis.
• Some diseases that cause inflammation don’t increase the sed rate. So a normal sed rate doesn’t always rule out a disease.
• Each lab has a different range for what’s normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn’t in the normal range may still be normal for you.