{"id":"carboxyhemoglobin","name":"Carboxyhemoglobin (COHb)","shortName":"COHb","aliases":["Carboxyhemoglobin","COHb","HbCO","Carboxyhemoglobin, Blood","CO-Hgb","Carbon Monoxide Hemoglobin","FCOHb","Carboxyhemoglobin %","Carboxyhemoglobin Quant","Carboxyhemoglobin Quantitation","COHgb","Carboxyhaemoglobin","Carboxy Hb","Carbon Monoxide Exposure, Blood"],"abbreviations":["COHb","HbCO","FCOHb","CO-Hb"],"loinc":[{"code":"20563-3","primary":true},{"code":"2032-1","primary":false},{"code":"2030-5","primary":false}],"specimen":"whole-blood","units":[{"ucum":"%","display":"%"},{"ucum":"1","display":"fraction (0–1)"}],"referenceRanges":[{"population":"Adults","low":0,"high":2,"unit":"%","unitDisplay":"%","note":"ARUP's interval for non-smokers is 0.0–2.0% (effective 2011). ARUP lists smokers separately: up to 5.0% at 1–2 packs a day and up to 9.0% at 3–4 packs a day. A study of 134 healthy adults measured 0.4–1.4% on venous blood. Reviews put non-smokers near 0.5% (1–2% in polluted cities) and smokers up to 8–10% or more. A German guideline calls 3–4% or more elevated, and notes that smokers can reach about 10% with no symptoms. The University of Iowa Hospitals list 1–3% for non-smokers and 4–8% for smokers. Labs set their own limits, so use the range printed on your report.","sources":[{"title":"Carboxyhemoglobin Quant (test 2005757)","url":"https://ltd.aruplab.com/Tests/Pub/2005757","publisher":"ARUP Laboratories"},{"title":"Reference intervals for venous blood gas measurement in adults","url":"https://doi.org/10.1515/cclm-2020-1224","publisher":"Clinical Chemistry and Laboratory Medicine 2021;59(5):947-954","year":2021},{"title":"S2k guideline diagnosis and treatment of carbon monoxide poisoning","url":"https://doi.org/10.3205/000300","publisher":"GMS German Medical Science 2021;19:Doc13","year":2021},{"title":"Carbon Monoxide Poisoning: From Occupational Health to Emergency Medicine","url":"https://doi.org/10.3390/jcm13092466","publisher":"Journal of Clinical Medicine 2024;13:2466","year":2024},{"title":"Carboxyhemoglobin (test CHB)","url":"https://www.healthcare.uiowa.edu/path_handbook/handbook/test388.html","publisher":"University of Iowa Hospitals & Clinics, Pathology Handbook"}]}],"review":{"status":"ai-verified","label":"AI-verified against cited sources. Awaiting expert review","lastReviewed":"2026-10-03"},"summary":"The share of your hemoglobin that is bound to carbon monoxide instead of oxygen. It shows recent carbon monoxide exposure, including from smoking.","url":"https://bloodtesttracker.com/markers/carboxyhemoglobin","notice":"Information, not medical advice. Ranges differ between labs, so the range on your own report is the one your result is judged against."}