Lead (Blood Lead)

What is Lead (Blood Lead)?

A blood lead test measures lead circulating in your blood, which reflects recent exposure plus lead released from bone.

A blood lead test measures the lead in a sample of your blood. It doesn't measure what sits in your bones, and it isn't a running total of everything you've ever absorbed. CDC's clinical teaching material says blood lead is more reflective of recent or ongoing exposures than of total body burden, and that most measurable levels are a mixture of current exposure and lead released from earlier exposure. The reason is bone. Adults store about 94% of their lead in bones and teeth (children about 73%), and the half-life of lead in adult blood has been estimated at 28 to 36 days. One result is a snapshot of recent weeks, with a contribution from a much slower reservoir. The number most people meet on a report is 3.5 µg/dL, and it's easy to misread. CDC set it in October 2021 as the 97.5th percentile of blood lead in U.S. children aged 1 to 5, using NHANES data from 2015-2016 and 2017-2018. It replaced the earlier value of 5 µg/dL. The same CDC report says the value "is not a health-based standard or a toxicity threshold." It's a statistical line: by construction, about 2.5% of children in that age group sit at or above it, and it moves whenever the national distribution moves. CDC also states that there is no known safe blood lead level in children. These two statements don't conflict. "No safe level" is a claim about biology. "3.5" is a claim about where a population distribution sits. Neither one tells you what your own number means. That depends on your age, pregnancy status, work, and history, and it's your clinician's call. For adults, the picture is split by purpose. NIOSH's workplace page (reviewed April 11, 2024) says the Council of State and Territorial Epidemiologists' blood lead reference value is 3.5 µg/dL, and notes that OSHA sets separate rules for workers exposed to lead on the job. Those are rules for employers and occupational clinicians. They aren't a scale for the rest of the population. Reading the report takes a little care. U.S. labs print micrograms per deciliter (µg/dL, sometimes "mcg/dL"). Outside the U.S. you may see µg/L, and 1 µg/dL equals 10 µg/L. Mayo Clinic Laboratories, for example, lists a reference range of <3.5 mcg/dL for its venous lead test, run by ICP-MS in a metal-free tube. A fingerstick or heel-stick (capillary) sample is a quick screen, but skin can carry environmental lead, so CDC's guidance says a capillary result at or above the reference value should be followed by a venous sample. A capillary number and a venous number are different kinds of result, so the sample type belongs next to the value. The reference value also tracks the country's progress. CDC reports that the geometric mean blood lead in children aged 1 to 5 fell from 15.2 µg/dL in 1976-1980 to 0.83 µg/dL in 2011-2016. For adults 20 and older, the NHANES geometric mean went from 1.09 µg/dL in 2011-2012 to 0.855 µg/dL in 2017-2018. A cutoff defined as the 97.5th percentile of that distribution gets lower as the whole distribution does. Pregnancy adds one more layer. CDC's teaching material notes that bone-to-blood lead mobilization increases during pregnancy and lactation. CDC's 2010 guidelines, written for clinicians, begin follow-up activities at 5 µg/dL in pregnant women and don't recommend blood lead testing for all pregnant women. The U.S. Preventive Services Task Force rated the evidence for screening asymptomatic pregnant people as insufficient in 2019 and has since said it won't update that recommendation. Those are statements to clinicians. They don't say anything about your result.

Typical reference context

The blood values describe populations or workplace rules. The water and food numbers describe what's in water or food, and they can't be compared to a result on your lab report. None of these tells you whether a particular person's result is acceptable.

What changed recently

The reference value hasn't changed. CDC lowered it to 3.5 µg/dL in October 2021, and the sources checked for this page show no later revision as of October 2026. E&E News reported in May 2025 that the whole staff of CDC's Childhood Lead Poisoning Prevention Program had been placed on administrative leave on April 1, 2025; the program's current status couldn't be confirmed.

The biggest recent story is food. FDA began investigating children's elevated blood lead in October 2023 and traced cinnamon applesauce pouches to lead chromate in cinnamon, which it called economically motivated adulteration. It had confirmed 90 cases at or above 3.5 µg/dL by January 31, 2024. Its ground cinnamon alert, first issued in 2024 and updated September 28, 2026, now lists 18 brands with 2.03 to 10.7 ppm lead in the spice. On January 6, 2025, FDA finalized action levels for processed baby and toddler food: 10 ppb for most categories, 20 ppb for single-ingredient root vegetables and dry infant cereals. FDA calls these guidance for industry, not directions to consumers.

In water, EPA's Lead and Copper Rule Improvements (October 30, 2024) lower the action level from 15 to 10 µg/L, require lead service line replacement within 10 years, and set a compliance date of October 30, 2027. As of October 2026 the rule is in court. American Water Works Association v. EPA (D.C. Circuit, No. 24-1376) was argued September 30, 2026, and EPA said in February 2026 that it will defend the rule.

Tests often checked alongside this

Lead is one of several metals on a heavy metal blood panel, which MedlinePlus (updated March 18, 2025) lists as most commonly including lead, mercury, arsenic, cadmium, and chromium. Methylmercury and fish are covered on Mercury (Blood Mercury).

What to ask your doctor

• Was my sample venous or capillary, and does a capillary result need a venous confirmation?
• Which reference value did this lab print, and which population is it written for?
• Given my home, job, hobbies, or pregnancy plans, which of these matter for how my result is read?
• If I've had lead results from other labs, are the units and sample types the same as this one?

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