The biotinidase test measures biotinidase enzyme activity in blood to detect biotinidase deficiency, an inherited condition that impairs recycling of the vitamin biotin. It’s used in newborn screening and to investigate unexplained neurological or skin issues (seizures, developmental delay, hair loss, rash). Early diagnosis permits simple lifelong biotin supplementation to prevent or reverse symptoms.

A serum biotin level test measures the amount of biotin (vitamin B7) in a blood sample to assess deficiency or excess. It's ordered when deficiency is suspected (hair loss, skin changes, neuropathy), to monitor supplementation, or if biotin might interfere with other laboratory assays. A routine venous blood draw is used; results are interpreted against lab-specific reference ranges and the patient’s clinical history.

Biotin (vitamin B7) blood tests are usually done privately. Typical costs range roughly $30–$200 in the United States, £30–£100 for private UK labs, and about INR 500–1,500 in India. Public systems (like the NHS) rarely offer routine biotin screening unless clinically indicated. Prices vary by lab, test type and whether insurance covers it—check local providers for exact pricing.

Normal biotinidase activity is generally defined as greater than 30% of mean serum activity. Profound deficiency is <10% activity and partial deficiency is 10–30% activity. Newborn screening reports percent of mean; specific numeric cutoffs can vary between laboratories, so low or borderline results usually prompt confirmatory testing and genetic evaluation.

Early signs of biotinidase deficiency, often appearing in infancy, include hypotonia, seizures, developmental delay, feeding difficulties, vomiting and failure to thrive. Characteristic dermatologic features are eczematous rash and alopecia. Affected infants may also have respiratory problems, conjunctivitis, and later risk of hearing or vision loss if untreated. Prompt diagnosis and biotin replacement prevent progression.

Biotinidase deficiency cannot be cured because it’s a genetic enzyme defect, but it is effectively managed with lifelong oral biotin (vitamin B7) supplementation. When started early—often after newborn screening—treatment prevents metabolic crises and allows normal development. Delayed or missed treatment can cause irreversible neurological damage or hearing loss, so adherence and regular monitoring are essential.