Lead is a heavy metal that is mostly found as a compound in the Earth’s crust. The largest use of lead in the present day and age is in batteries of cars.
The reference ranges for lead are as follows:
Normal levels in children: < 10 μg/dL (If screening test at 6 months shows more than 2 μg/dL, repeat testing is warranted in 1 year and exposure prevention strategies should be initiated.)
Normal levels in adult: < 25 μg/dL
The Centers for Disease Control considers children to have an elevated level of lead if the amount of lead in the blood is at least 10 μg/dL.
Medical evaluation and environmental investigation and remediation should be done for all children and adults with blood lead levels equal to or greater than 20 μg/dL.
Medical treatment (ie, chelation therapy) may be necessary in children or adults if the lead concentration in blood is higher than 45 μg/dL. 
Collection and Panels
Lead is generally measured in whole blood rather than in serum or plasma, because most of the circulating lead is bound within the blood cells and is present as erythrocyte protoporphyrin.
Lead levels may be determined directly using atomic absorption spectroscopy, inductively coupled plasma/mass spectrometry (ICP/MS), or anode stripping voltammetry (ASV). These analytical techniques involve atomization of the blood sample and further quantification by the mass spectrophotometer, voltaic cell set up in ASV, and the total current associated with the stripping of the metal is proportional to the concentration of that metal. 
Lead is a heavy metal that is mostly found as a compound in the earth’s crust. The largest use of lead in the present day and age is in batteries of cars.
Lead can enter the environment through releases from mining lead and other metals, and from factories that make or use lead, lead alloys, or lead compounds. Lead is released into the air during burning coal, oil, or chipping of lead based paint from buildings, bridges, and other structures.
Humans acquire lead through swallowing. The amount that eventually circulates in the blood stream depends on the compound’s absorption from the stomach. If adults and children swallow the same amount of lead, a bigger proportion of the amount swallowed will enter the blood in children (50%) than in adults.
Lead is found bound as a complex with amino acids and nonprotein thiols in the blood stream and neurotoxic metabolites are generated after tetraethyl lead and tetramethyl lead undergo oxidative dealkylation in the liver.
Absorbed inorganic lead is excreted in feces and urine.
The CDC recommends that the states test children as follows:
At ages 1 and 2 years
At ages 3–6 years if they have never been tested for lead
If they receive services from public assistance programs for the poor such as Medicaid or the Supplemental Food Program for Women, Infants, and Children
If they live in a building or frequently visit a house built before 1950
If they visit a home (house or apartment) built before 1978 that has been recently remodeled; and/or
If they have a brother, sister, or playmate who has had lead poisoning.
Adults should be tested if they work in an environment with lead exposure or who exhibit signs and symptoms of lead poisoning (encephalopathy, seizures, foot drop and wrist drop).
Lead has a short circulating half-life in blood, and, although lead levels are a reliable indicator of recent lead exposure, they may not be wholly accurate. Cumulative lead burden can be estimated with use of in vivo X-ray fluorescence.