Sign in →

Test ID: HTR2V Serotonin Receptor Genotype (HTR2A and HTR2C), Varies

Specimen Required

Multiple genotype tests can be performed on a single specimen after a single extraction. See Multiple Genotype Test List in Special Instructions for a list of tests that can be ordered together.


Submit only 1 of the following specimens:


Specimen Type: Whole blood

Container/Tube: Lavender top (EDTA)

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in original tube.

Specimen Stability Information: Ambient (preferred)/Refrigerated


Specimen Type: Saliva

Patient Preparation: Patient should not eat, drink, smoke, or chew gum 30 minutes prior to collection.

Supplies: DNA Saliva Collection Kit (T786)

Container/Tube: Saliva Swab Collection Kit

Specimen Volume: 1 swab

Collection Instructions: Collect and send specimen per kit instructions.

Specimen Stability Information: Ambient


Specimen Type: DNA

Container/Tube: 2 mL screw top tube

Specimen Volume: 100 mcL (microliters)

Collection Instructions:

1. The preferred volume is 100 mcL at a concentration of 50 ng/mcL.

2. Include concentration and volume on tube.

Specimen Stability Information: Frozen (preferred)/Ambient/Refrigerated


1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available in Special Instructions:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. If not ordering electronically, complete, print, and send a Pharmacogenomics Test Request (T797) with the specimen.

Useful For

Guiding treatment choice of antidepressant


Guiding treatment choice in individuals who have a drug-metabolizer phenotype discordant with CYP450 genotypes


Identifying those patients at risk of excessive weight gain or metabolic syndrome when receiving antipsychotic medications

Method Name

Real-Time Polymerase Chain Reaction (PCR) with Allelic Discrimination Analysis

Reporting Name

HTR2A/2C Genotype

Specimen Type


Specimen Minimum Volume

Blood: 0.4 mL
Saliva: 1 swab

Specimen Stability Information

Specimen Type Temperature Time
Varies Varies

Clinical Information

Treatment with specific antidepressant and antipsychotic medications is often guided empirically. Despite the wide array of drugs available for treatment, some patients do not initially respond to treatment and others who respond early may eventually relapse or develop serious side effects. Antidepressant selection may be more effectively guided by genotyping polymorphic genes encoding several cytochrome P450 enzymes, the serotonin transporter, and the serotonin (5-hydroxytryptamine) receptors HTR2A and HTR2C.(1)


Drugs that bind to the serotonin receptors have a wide range of effects including altering the activation of the receptors, rendering them more or less sensitive to drug concentration, or blocking the receptor. Variations (polymorphisms) in the genes that encode for the serotonin receptor have been associated with different types of drug responses including:

-Allelic variation in the HTR2A gene has been reported to affect response to the selective serotonin reuptake inhibitor (SSRI) citalopram. Alternate antidepressant medications may be considered for patients predicted to respond poorly to citalopram due to polymorphic variants in the HTR2A serotonin receptor.(2) Associations between other antidepressants and response based on HTR2A genotype have been reported, but are less consistent in the literature.

-Treatment with antipsychotics results in significant weight gain (2-3 kg/m[2]) in some patients. Weight gain has been positively correlated with the c.-759C->T polymorphism in the promoter of HTR2C(3) and metabolic syndrome has been associated with c.551-3008C->G.(4)


The following table displays the HTR2A/2C variants detected by this assay:



cDNA Nucleotide Change










Reference Values

An interpretive report will be provided.


An interpretive report will be provided.


For additional information regarding pharmacogenomic genes and their associated drugs, see Pharmacogenomics Associations Tables in Special Instructions. This resource also includes information regarding enzyme inhibitors and inducers, as well as potential alternate drug choices.

Clinical Reference

1. Malhotra AK, Murphy GM Jr, Kennedy JL: Pharmacogenetics of psychotropic drug response. Am J Psychiatry 2004;161(5):780-796

2. McMahon FJ, Buervenish S, Charney D et al: Variation in the gene encoding the serotonin 2A receptor is associated with outcome of antidepressant treatment. Am J Hum Genet 2006;78:804-814

3. Reynolds GP, Zhang ZJ, Zhang XB: Polymorphism of the promoter region of the serotonin 5-HT2C receptor gene and clozapine-induced weight gain. Am J Psychiatry 2003;160:677-679

4. Mulder H, Cohen D, Scheffer H, et al: HTR2C gene polymorphisms and the metabolic syndrome in patients with schizophrenia. J Clin Psychopharmacol 2009;29:16-20

Day(s) and Time(s) Performed

Monday through Friday; 8 a.m.

Analytic Time

3 days (not reported on Saturday or Sunday)

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

0033U-Unlisted molecular pathology procedure

LOINC Code Information

Test ID Test Order Name Order LOINC Value
HTR2V HTR2A/2C Genotype 46726-6


Result ID Test Result Name Result LOINC Value
BA0220 HTR2A rs7997012 Genotype In Process
BA0221 HTR2C rs3813929 Genotype 75732-8
BA0222 HTR2C rs1414334 Genotype In Process
BA0223 Interpretation 69047-9
BA0224 Additional Information 48767-8
BA0225 Method 49549-9
BA0226 Disclaimer 62364-5
BA0227 Reviewed by 18771-6
Mayo Clinic Laboratories | Genetics and Pharmacogenomics Catalog Additional Information: