Lead in the human body can be measured in blood, urine, bones, teeth, or hair. The most frequent test is to measure the blood Lead level (BLL). Measuring an individual's blood Lead level (BLL) can detect Lead poisoning in adults or children. Red blood cells increase erythrocyte protoporphyrin (EP) when blood Lead is high.

BLL measurements show the amount of Lead circulating in the blood stream, not the amount of Lead stored in the body. BLLs do not show either the current, or cumulative effects of Lead on a person's body.

Blood Lead levels are reported in micrograms per deciliter (µg/dl), or micrograms per 100 grams (µg/100 g) of whole blood, which is approximately equal to µg/dl.

The standard elevated blood Lead level (BLL) for adults' set by the Center for Disease Control is 25 micrograms per deciliter (25 µg/dl) of whole blood. This level recognizes that every adult has accumulated some Lead contamination.
The level for a child is much lower, currently it is 10 micrograms per deciliter (10 µg/dl) of blood.

Body burden of Lead increases from birth to old age. Total Lead content in 60-70 year old men may reach more than 200 mg with about 95% residing in the bone.. Lead is also excreted in human milk in concentrations up to 12 ug/l. Workers exposed to Lead should have blood Lead levels below 40 micrograms/dL. Treatment is recommended if the level exceeds 80 micrograms/dL.

Blood Lead Levels in Children

The Center for Disease Control recommends that all children be screened for Lead poisoning yearly. This is especially important for children between 6 months and 6 years of age.

Children with an EP of 35 micrograms per deciliter should be tested for a blood Lead level.
Children with a BLL of 20 micrograms per deciliter or higher should be screened by their doctor for Lead poisoning.
Medical treatment is necessary if the BLL is higher than 45 micrograms per deciliter

How the test is performed
Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell with blood.
A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
The blood is collected and transported in containers that do not contain Lead. It is usually evaluated by atomic absorption spectrometer.