Blood lead level is a test that measures the amount of lead in the blood.

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.

No special preparation is needed.

If your child is to have this test performed, it may be helpful to explain how the test will feel, and even demonstrate on a doll. Explain the reason for the test. Knowing the "how and why" may reduce the anxiety your child feels.

When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.

This test is used to screen people at risk for lead poisoning, including industrial workers and children who live in urban areas. It is also used to see if treatment for lead poisoning is working.

While lead serves no function in our bodies, it is usually found in the body in some amount since it is so common in the environment. Low levels in adults are not thought to be harmful, but in infants and children, low levels of lead can lead to toxicity that may cause deficits in intellectual or cognitive development.

See: Lead poisoning

Adults:

• Less than 20 micrograms/dL of lead in the blood

Children:

• Less than 10 micrograms/dL of lead in the blood

Note: dL = deciliter

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

Adults who have been exposed to lead should have blood lead levels below 40 micrograms/dL. Treatment is recommended if you have symptoms of lead poisoning, or if your blood lead level is greater than 60 micrograms/dL.

In children, a blood lead level greater than 10 micrograms/dL requires further testing and monitoring. The source of lead must be found and removed. A lead level greater than 45 micrograms/dL in a child's blood usually indicates the need for treatment.

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)

Woolf AD, Goldman R, Bellinger DC. Update on the clinical management of childhood lead poisoning. Pediatr Clin North Am. 2007;54: 271-294.

McGuigan MA. Chronic poisoning: trace metals and others. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007: chap 20.