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Mercury/Creatinine Ratio, Urine

Mercury in a urine sample shown per gram of creatinine, so the result is not thrown off by how dilute your urine is.

AI-verified against cited sources. Awaiting expert reviewAlso called Hg/CrLOINC 13465-0

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What it is

This test measures mercury in a random (spot) urine sample and divides it by creatinine, a waste product your body makes at a steady rate. Dividing by creatinine evens out the difference between watery and concentrated samples. Urine mostly reflects inorganic and elemental mercury, such as vapor from spills, some industrial work and small amounts from dental amalgam fillings. Mercury from fish is better measured in blood.

Why it matters

Ongoing contact with elemental or inorganic mercury can affect the nervous system and the kidneys. A creatinine-corrected urine result is a common way to follow that kind of exposure over time, including for workplace monitoring. For recent exposure, and for mercury from fish, a blood test is the better choice.

If it’s high

A higher result means more mercury is leaving your body than is typical. That can be a sign of contact with inorganic or elemental mercury. A contaminated sample can also give an unexpected result, so a repeat test is sometimes reasonable. How a given level affects a person varies a lot.

Common causes

  • A sample contaminated by skin, dust or a container that was not trace-element-free
  • Dental amalgam (silver) fillings, which usually add only a small amount
  • Work that involves mercury, such as dentistry, gold mining or some manufacturing
  • Broken thermometers, gauges or other liquid mercury spills
  • Some skin-lightening creams and traditional remedies that contain mercury
  • A sample collected after a chelating medicine

What can help

  • Ask your clinician whether the result fits your history, and whether to repeat it in a certified trace-element-free container
  • If you work with mercury, ask about workplace exposure monitoring and protective equipment
  • Follow local public-health guidance for cleaning up liquid mercury spills
  • Check skin-lightening creams and traditional remedies for mercury on the label
  • Ask whether a blood mercury test would add information, especially if you eat a lot of fish

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

For adults: up to 2 µg/g creatinine. Source: Mayo Clinic Laboratories (via the testcatalog.org mirror), ARUP Laboratories.

What can affect your result

  • How dilute or concentrated your urine is, which the creatinine correction tries to even out
  • Seafood in the days before collection
  • Recent contrast dye (gadolinium or iodine)
  • The number of dental amalgam fillings
  • Work, hobby or home exposure to mercury
  • The collection container and how the sample was kept
  • Seafood in the 2 to 3 days before collection. ARUP asks you to avoid shellfish and seafood for 48 to 72 hours.
  • Gadolinium or iodine contrast dye can interfere with this kind of metal test. Mayo Clinic Laboratories asks for a 96-hour wait after contrast, and ARUP asks for at least 72 hours (14 days if kidney function is reduced).
  • A sample contaminated by skin, dust or a container that is not certified trace-element-free can read falsely high. Labs may ask for a repeat in a certified container.
  • Urine collected after a chelating (metal-binding) medicine, called a provoked or challenge test, has no valid reference range.
  • A single (spot) urine sample can vary a lot through the day, which is why the mercury result is divided by creatinine.
  • ARUP lists diet, supplements, vitamins and minerals as possible sources of interference. Ask your clinician before stopping anything.

Weeks to months. Inorganic mercury leaves the body slowly.

When to talk to a clinician

Talk with your clinician soon if your result is above your lab's range, especially if you work with mercury or have a tremor, unusual irritability, memory or sleep trouble, heavy drooling or gum problems. If you may have breathed vapor from a large mercury spill and feel unwell, seek urgent care.

Questions you could ask

  • Which mercury test fits my situation best: urine, blood or a 24-hour collection?
  • Could my job, hobbies or home be a source of mercury?
  • Should we repeat the test in a certified trace-element-free container?
  • Would a blood mercury test add anything for me?

Questions people ask

Why is my result shown per gram of creatinine?

Urine can be more watery or more concentrated from one sample to the next. Creatinine is released at a steady rate, so dividing mercury by creatinine makes samples easier to compare.

Why do Mayo Clinic Laboratories and ARUP use such different limits?

Mayo lists less than 2 µg/g creatinine for adults, while ARUP lists up to 20 µg/g. Labs choose their limits differently. Compare your result with the range printed on your own report, and ask your clinician how to read it.

What is a provoked urine mercury test?

It is a urine test collected after taking a chelating medicine. Normal ranges don't apply to those samples, and the American College of Medical Toxicology recommends against using them. Talk with your clinician if one was suggested to you.

Show the science and sources

Units

  • 1 µg/g creatinine = 1 µg/g creatinine
  • 1 µg/g creatinine = 0.1131 µg/mmol creatinine

Open the Urine Mercury/Creatinine unit converter

For clinicians and researchers

Random urine mercury by triple-quadrupole ICP-MS with creatinine measured on the same sample by an enzymatic colorimetric assay (Mayo Clinic Laboratories HGUCR). Urine mercury predominantly reflects elemental and inorganic mercury; ARUP prefers whole blood for assessing acute exposure. Reference limits differ about tenfold between labs: Mayo below 2 µg/g creatinine in adults, ARUP up to 20.0 µg/g (and 5.0 µg/L). ARUP states that unexposed people are typically below 10 µg/L in urine and that elevated results may reflect skin or collection contamination, and it recommends confirming with a second specimen in a certified trace-element-free container. Mayo also offers a separate occupational-exposure test that applies a workplace biological exposure index instead of this reference limit. Post-chelator challenge urine has no valid reference range, and the American College of Medical Toxicology recommends against that testing. Creatinine correction is less reliable in very dilute or very concentrated urine, and the µg/mmol conversion uses creatinine's molecular weight of 113.12 g/mol.

LOINC 13465-0 (primary), 22680-3. Specimen: urine.

Sources

  1. Mercury/Creatinine Ratio, Random, Urine (test HGUCR), Mayo Clinic Laboratories (via the testcatalog.org mirror)
  2. Mercury, Random Urine (test 2011481), ARUP Laboratories
  3. ACMT Recommends Against Use of Post-Chelator Challenge Urinary Metal Testing, American College of Medical Toxicology (Journal of Medical Toxicology) (2017)
  4. Creatinine (compound summary), PubChem, National Library of Medicine

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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