This private blood test measures plasma homocysteine, an amino acid intermediate sensitive to folate (vitamin B9), vitamin B12 and vitamin B6 status as well as MTHFR methylation pathways. The catalogue test price is £126.25 plus a £50 phlebotomy fee, with results in 1 day.
Because homocysteine rises if red blood cells remain in contact with plasma after collection, having your venous blood drawn directly at 117a Harley Street ensures immediate separation and accurate laboratory measurement.
Written by Mr Stephen Lingam. Reviewed by Prof Darrel Francis (GMC 4062833) on 18/10/2026.
Red blood cells continue to release homocysteine into the sample after collection unless the plasma is centrifuged and separated promptly, making in-clinic venous sampling much more reliable than postal finger-prick kits.
An overnight fast (or avoiding a high-protein meal for 8 to 12 hours before your blood draw) is recommended because protein-rich meals can transiently raise plasma homocysteine.
Results are normally returned in 1 working day.
Clinicians commonly pair homocysteine with active vitamin B12, serum folate, methylmalonic acid and a full lipid or cardiovascular risk panel under the same £50 phlebotomy fee.