Editing Biotin (section)

===Diagnosis===
Low serum and urine biotin are not sensitive indicators of inadequate biotin intake.<ref name=PKIN2020Biotin /> However, serum testing can be useful for confirmation of consumption of biotin-containing dietary supplements, and whether a period of refraining from supplement use is long enough to eliminate the potential for interfering with drug tests.<ref name=Luong2019/><ref name=Bowen2019/> Indirect measures depend on the biotin requirement for carboxylases. [[3-Methylcrotonyl-CoA]] is an intermediate step in the catabolism of the amino acid [[leucine]]. Without biotin, the pathway diverts to [[3-hydroxyisovaleric acid]]. Urinary excretion of this compound is an early and sensitive indicator of biotin deficiency.<ref name="DRItext" /><ref name=PKIN2020Biotin />