== Interpretation ==
In general, a healthy individual has a value of <math>D_{L_{CO}}</math> between 75% and 125% of the average.<ref name=uppsala>LUNGFUNKTION - Practice compendium for semester 6. Department of Medical Sciences, Clinical Physiology, Academic Hospital, Uppsala, Sweden. Retrieved 2010.</ref> However, individuals vary according to age, sex, height and a variety of other parameters. For this reason, reference values have been published, based on populations of healthy subjects<ref>{{cite journal |vauthors=Miller A, Thornton JC, Warshaw R, Anderson H, Teirstein AS, Selikoff IJ | year = 1983 | title = Single breath diffusing capacity in a representative sample of the population of Michigan, a large industrial state. Predicted values, lower limits of normal, and frequencies of abnormality by smoking history | url = | journal = Am Rev Respir Dis | volume = 127 | issue = 3| pages = 270–7 | pmid = 6830050 | doi = 10.1164/arrd.1983.127.3.270 | doi-broken-date = 2020-0810-3110 }}</ref><ref>{{cite journal |vauthors=Knudson RJ, Kaltenborn WT, Knudson DE, Burrows B | year = 1987 | title = The single-breath carbon monoxide diffusing capacity. Reference equations derived from a healthy nonsmoking population and effects of hematocrit | url = | journal = Am Rev Respir Dis | volume = 135 | issue = 4| pages = 805–11 | pmid = 3565929 | doi=10.1164/arrd.1987.135.4.805}}</ref><ref>{{cite journal |vauthors=Cotes JE, Chinn DJ, Quanjer PH, Roca J, Yernault JC | year = 1993 | title = Standardization of the measurement of transfer factor (Diffusing capacity) | url = | journal = Eur Respir J Suppl | volume = 16 | issue = | pages = 41–52 | pmid = 8499053 | doi = 10.1183/09041950.041s1693 | s2cid = 54555111 }}</ref> as well as measurements made at altitude,<ref>{{cite journal |vauthors=Crapo RO, Morris AH, Gardner RM | year = 1982 | title = Reference values for pulmonary tissue volume, membrane diffusing capacity, and pulmonary capillary blood volume | url = | journal = Bull Eur Physiopathol Respir | volume = 18 | issue = 6| pages = 893–9 | pmid = 6927541 }}</ref> for children<ref>{{cite journal |vauthors=Koopman M, Zanen P, Kruitwagen CL, van der Ent CK, Arets HG | year = 2011 | title = Reference values for paediatric pulmonary function testing: The Utrecht dataset | url = | journal = Respir. Med. | volume = 105 | issue = 1| pages = 15–23 |pmid=20889322 | doi=10.1016/j.rmed.2010.07.020}} Erratum in ''Respir. Med.'' 2011 Dec;105(12):1970-1.</ref> and some specific population groups.<ref>{{cite journal |vauthors=Chin NK, Ng TP, Hui KP, Tan WC | date = Jun 1997 | title = Population based standards for pulmonary function in non-smoking adults in Singapore | url = | journal = Respirology | volume = 2 | issue = 2| pages = 143–9 | pmid = 9441128 | doi=10.1111/j.1440-1843.1997.tb00070.x| s2cid = 31037816 }}</ref><ref>{{cite journal |vauthors=Piirilä P, Seikkula T, Välimäki P | year = 2007 | title = Differences between Finnish and European reference values for pulmonary diffusing capacity | url = | journal = Int J Circumpolar Health | volume = 66 | issue = 5| pages = 449–57 | pmid = 18274210 | doi = 10.3402/ijch.v66i5.18316 | s2cid = 22302973 }}</ref><ref>{{cite journal |vauthors=Ip MS, Lam WK, Lai AY, etal | title = Hong Kong Thoracic Society. Reference values of diffusing capacity of non-smoking Chinese in Hong Kong | url = | journal = Respirology | volume = 12 | issue = 4| pages = 599–606 | doi = 10.1111/j.1440-1843.2007.01084.x | pmid = 17587430 | date=July 2007| s2cid = 5897844 }}</ref>
===Blood CO levels may not be negligible===
|