Chemical Pathology


Homocysteine is a product of the metabolism of the amino acid methionine, a process requiring folic acid (folate) and, for folate to remain in its active form, vitamin B12.

Routine screening of homocysteine is not recommended, however this test may be appropriate:-

  • In the investigation of younger patients with premature vascular disease in whom there are no obvious risk factors.
  • Investigation for suspected infantile homocystinuria
  • Confirmation of vitamin B12 deficiency when B12 level borderline (NB: not routinely available for this purpose)

Sample requirements

For adults, blood taken into a 4mL EDTA tube sent on ICE immediately to the laboratory (no need to fast for this test). Please telephone to alert the laboratory before collecting the blood to ensure prompt sample handling.

EDTA with cap

For children, blood taken into a 2mL EDTA tube sent on ICE immediately to the laboratory.

2ml EDTA tube


Do not store. Sample (on ice) must be rushed immediately to the laboratory as plasma must be removed from the red blood cells within 30 minutes.

Required information

Relevant clinical details including reason for the request.

Turnaround times

The samples are sent for analysis to Guy's and St Thomas' Hospital, London with results expected back within 3 weeks.

Reference ranges

0-15 umol/L

Note: Undetectable homocysteine levels have been observed in patients with molybdenum cofactor deficiency or isolated sulphite oxidase deficiency. Therefore in infants with clinical features compatbile with these conditions (e.g. intractable seizures or abnormal movements of uncertain cause), homocysteine levels of <2.0 umol/L may warrant additional testing (blood urate and sulphocysteine).

Further information

To learn more about homocysteine visit Lab Tests Online

or access the analyte monograph of the Association for Clinical Biochemistry and Laboratory Medicine

Page last updated: 04/02/2019