Clinics and Departments

Laboratory Services

Lab Dept:


Test Name:


General Information

Lab Order Codes:



Amino Acid Homocysteine

CPT Codes:

83090 - Homocysteine

Test Includes:

Homocysteine, Total, Plasma measured in mcmol/L.


Test Indications:

As an aid for screening patients suspected of having an inherited disorder of methionine metabolism including:
● Cystathionine beta-synthase deficiency (homocystinuria)
● Methylenetetrahydrofolate reducase deficiency (MTHFR) and its thermolabile variants
● Methionine synthase deficiency
● Cobalamin (Cbl) metabolism
● Combined methyl –Cbl and adenosyl-Cbl deficiencies: Cb lC2, Cbl D2, and Cbl F3
● Methyl-Cbl specific deficiencies: Cbl D-Var1, Cbl E, ;and Cbl G deficiencies
● Transcobalamin II deficiency
● Adenosylhomocysteinase (AHCY) deficiency
● Glycine N-methyltransferase (GNMT) deficiency
● Methionine adenosyltransferase (MAT) I/III deficiency

Lab Testing Sections:

Chemistry - Sendouts

Referred to:

Mayo Medical Laboratories (MML Test:80379/HCYSP)

Phone Numbers:

MIN Lab: 612-813-6280

STP Lab: 651-220-6550

Test Availability:

Daily, 24 hours

Turnaround Time:

2 - 5 days, test set-up Monday – Friday

Special Instructions:

See Patient Preparation


Specimen Type:



Lavender top (EDTA) tube

Draw Volume:

1.2 mL (Minimum: 0.5 mL) blood

Processed Volume:

0.4 mL (Minimum: 0.15 mL) plasma


Routine venipuncture from fasting patient. Mix sample by gentle inversion. Place specimen on wet ice and deliver to the lab for immediate processing.

Special Processing:

Lab Staff: Centrifuge specimen within 4 hours of draw. A refrigerated centrifuge is not required if the 4-hour time restraint is met. Alternatively, if blood is not immediately placed on ice, plasma must be removed from cells within 1 hour of draw.

Remove plasma aliquot into a screw-capped round bottom plastic vial. Store and ship at refrigerated temperatures. Forward promptly.

Patient Preparation:

Patient should be fasting (if possible and not required) prior to specimen collection. A 4 hour fast is preferred.

Sample Rejection:

Warm specimens; mislabeled or unlabeled specimens


Reference Range:

Adults: < or =13 mcmol/L
Reference values apply to fasting specimens only.

Homocysteine levels of >13 mcmol/L are considered abnormal, in patients under evaluation for Cardiovascular disease and Neurovascular disease.

Hyperhomcysteinemia suggests that genetic and nutritional factors are potentially involved in the etiology of the disease.

Response to dietary treatment can be evaluated by monitoring plasma homocysteine levels over time.

Critical Values:



A fasting specimen is recommended; however, non-fasting homocysteine concentrations produce slightly higher, but clinically insignificant changes.

Other factors that may influence and increase plasma homocysteine include: Age, Smoking, Poor diet/cofactor deficiencies, Chronic kidney disease/renal disease, hypothyroidism


Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) Stable Isotope Dilution


Mayo Medical Laboratories Web Page October 2014


11/16/2010: Units change from umol/L to mcmol/L.

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