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Paediatric Laboratory Medicine

Formic Acid

Clinical Significance

Methanol is metabolized to formic acid (which is present as the formate ion) via formaldehyde in a process initiated by the enzyme alcohol dehydrogenase in the liver. Methanol is converted to formaldehyde via alcohol dehydrogenase (ADH) and formaldehyde is converted to formic acid (formate) via aldehyde dehydrogenase (ALDH). The conversion to formate via ALDH proceeds completely, with no detectable formaldehyde remaining. Formate is toxic because it inhibits mitochondrial cytochrome c oxidase, causing the symptoms of hypoxia at the cellular level, and also causing metabolic acidosis, among a variety of other metabolic disturbances. The ocular injury caused by methanol may be due to retinal injury, which results from intra-retinal metabolism of methanol and the accumulation of formic acid. Alternatively, it may be caused be the inhibition of normal metabolism in optic nerve cells.

Test Name

Formic Acid

Alternate Name/ Synonym


Test Code


Drug Class

Toxic Metabolite



External Proficiency Testing


Turn Around Time

Daily, Stat

Specimen Type

Serum, Plasma (Heparin, Citrate or EDTA)

Minimum Specimen Requirements

400 uL


4°C (transport with a cool pack if possible)

Special Requirements

Method: GC-HS-FID

Approval is not required

CPT Codes


Shipping and Contact Information

The Hospital for Sick Children
Rapid Response Laboratory
170 Elizabeth Street, Room 3642
Toronto, ON
M5G 2G3
Phone: 416-813-7200
Phone: 1-855-381-3212

Therapeutic Range

Not Detected

Critical Values

Formic Acid: > 3.3 mmol/L