What you carry at this position in your DNA and what research says about it.
Antipsychotic Weight Gain: 6/10 evidence, 26 publications.
You're viewing every possible genotype for this variant.
None of these is your result. Use the genotype toggle to compare them, then sign up and upload your DNA to see which one is yours.
Sample genotype (not yours): C/C
Higher Antipsychotic Weight Gain Risk
Gaining weight during treatment with certain antipsychotic medications is more likely with this genotype. It also correlates with an increased risk of developing metabolic syndrome during therapy.
What this genotype means: Higher risk of weight gain from antipsychotics; Increased risk of metabolic syndrome.
Sample genotype (not yours): C
Gaining weight during treatment with certain antipsychotic medications is more likely with this single-allele genotype in males. It also correlates with an increased risk of developing metabolic syndrome during therapy.
Sample genotype (not yours): C/T
Lower Antipsychotic Weight Gain but Higher Migraine Risk
A lower risk of gaining weight during treatment with certain antipsychotic medications is associated with this heterozygous genotype. However, it also correlates with a higher susceptibility to developing migraines.
What this genotype means: Lower risk of weight gain from antipsychotics; Higher risk of migraines.
Sample genotype (not yours): T
A lower risk of gaining weight during treatment with certain antipsychotic medications is associated with this single-allele genotype in males. However, it also correlates with a higher susceptibility to developing migraines.
Sample genotype (not yours): T/T
A lower risk of gaining weight during treatment with certain antipsychotic medications is associated with this genotype. However, it also correlates with a higher susceptibility to developing migraines.
Gene function and biological role
Gene Function: The HTR2C gene encodes the 5-hydroxytryptamine receptor 2C, a key serotonin receptor subtype widely expressed in the central nervous system [1]. This receptor plays a critical role in regulating appetite, energy balance, and mood [2]. Serotonin binding to this receptor normally signals satiety, helping to control food intake and prevent overeating [3]. Because of its central role in metabolic regulation, genetic variations in this gene are heavily studied in relation to obesity and metabolic side effects of medications [4].
Variant Impact: The rs3813929 variant, also known as -759C/T, is located in the promoter region of the HTR2C gene [2]. This genetic change alters the transcription rate and promoter activity of the serotonin 2C receptor [5]. Research indicates that the T allele disrupts specific DNA-protein interactions in the hypothalamus, leading to altered receptor expression [2]. This functional alteration directly influences how the brain responds to serotonin and certain medications that block these receptors [1].
Key Insight: The same genetic variant that protects against antipsychotic-induced weight gain also increases the risk of developing migraines due to altered serotonin receptor activity.
Location: HTR2C. Chromosome X · Xq23 · 114.6 Mb
Estimated prevalence by population
Global 76.5%; European 68.7%; African 94.1%; East Asian 75.3%; South Asian 53.4%; Americas 73.4%; Ashkenazi 72.9%; Finnish 72.4%; Middle Eastern 77.9%; Amish 94.2%.
Estimated CC genotype frequency.
Global 21.5%; European 28.4%; African 5.8%; East Asian 22.9%; South Asian 39.4%; Americas 24.6%; Ashkenazi 25.0%; Finnish 25.4%; Middle Eastern 20.7%; Amish 5.7%.
Estimated CT genotype frequency.
Global 2.1%; European 2.9%; African 0.1%; East Asian 1.7%; South Asian 7.3%; Americas 2.1%; Ashkenazi 2.1%; Finnish 2.2%; Middle Eastern 1.4%; Amish 0.1%.
Estimated TT genotype frequency.
Showing effects for C/C genotype
Pharmacogenomics
Antidepressant & Psychiatric Drug Response
Antipsychotic Weight Gain. Evidence: 6/10. Source: PMID 15666332. Increased Risk.
Neurology & Mental Health
Headache & Migraine
Migraine. Evidence: 6/10. Typical Risk.
Cardiovascular & Metabolic
Metabolic Syndrome & Insulin Resistance
Metabolic Syndrome. Evidence: 4/10. Source: PMID 19142101. Increased Risk.
Obesity & Body Composition
Body Mass Index. Evidence: 3/10. Source: PMID 20065966. Typical BMI.
Showing effects for C genotype
Showing effects for C/T genotype
Antipsychotic Weight Gain. Evidence: 6/10. Source: PMID 15666332. Decreased Risk.
Migraine. Evidence: 6/10. Increased Risk.
Metabolic Syndrome. Evidence: 4/10. Source: PMID 19142101. Decreased Risk.
Body Mass Index. Evidence: 3/10. Source: PMID 20065966. Borderline Higher.
Showing effects for T genotype
Showing effects for T/T genotype
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Clinical studies show that psychiatric patients with this genotype are more susceptible to substantial weight gain when prescribed medications like olanzapine or risperidone [1]. This susceptibility is thought to stem from reduced promoter activity of the serotonin 2C receptor, which impairs normal satiety signaling [2]. Research indicates that the common C allele does not offer the protective barrier against metabolic side effects seen with the T allele [3]. Consequently, monitoring metabolic parameters is often emphasized by clinicians when these medications are used [4]. Additionally, this genotype is associated with a lower risk of developing migraines compared to those carrying the T allele.
Higher risk of weight gain from antipsychotics; Increased risk of metabolic syndrome.
Sample genotype: C (Single copy)
Clinical studies in male patients show a higher susceptibility to substantial weight gain when prescribed medications like olanzapine or risperidone [1]. This susceptibility is thought to stem from reduced promoter activity of the serotonin 2C receptor, which impairs normal satiety signaling [2]. Research indicates that the common C allele does not offer the protective barrier against metabolic side effects seen with the T allele [3]. Consequently, monitoring metabolic parameters is often emphasized by clinicians when these medications are used [4]. Additionally, this single-allele genotype is associated with a lower risk of developing migraines compared to those carrying the T allele.
Sample genotype: CT (Heterozygous)
Clinical studies show that psychiatric patients with this genotype have a reduced likelihood of substantial weight gain when prescribed medications like olanzapine or risperidone [1]. This protective effect is thought to stem from increased promoter activity of the serotonin 2C receptor, which helps maintain normal satiety signaling [2]. Research indicates that carrying at least one T allele offers a protective barrier against metabolic side effects [3]. Consequently, metabolic risks may be lower, though clinical monitoring remains important [4]. Additionally, this genotype is associated with a higher risk of developing migraines compared to those with the CC genotype.
Lower risk of weight gain from antipsychotics; Higher risk of migraines.
Sample genotype: T (Single copy)
Clinical studies in male patients show a reduced likelihood of substantial weight gain when prescribed medications like olanzapine or risperidone [1]. This protective effect is thought to stem from increased promoter activity of the serotonin 2C receptor, which helps maintain normal satiety signaling [2]. Research indicates that carrying the T allele offers a protective barrier against metabolic side effects [3]. Consequently, metabolic risks may be lower, though clinical monitoring remains important [4]. Additionally, this single-allele genotype is associated with a higher risk of developing migraines compared to those with the C genotype.
Sample genotype: TT (Homozygous)
Clinical studies show that psychiatric patients with this genotype have a reduced likelihood of substantial weight gain when prescribed medications like olanzapine or risperidone [1]. This protective effect is thought to stem from increased promoter activity of the serotonin 2C receptor, which helps maintain normal satiety signaling [2]. Research indicates that carrying two T alleles offers a protective barrier against metabolic side effects [3]. Consequently, metabolic risks may be lower, though clinical monitoring remains important [4]. Additionally, this genotype is associated with a higher risk of developing migraines compared to those with the CC genotype.
Variants with shared genetic architecture
rs6318 · HTR2C Gene · Chr X · Stress and Heart Health
rs1414334 · HTR2C Gene · Chr X · Antipsychotic Metabolic Risk
rs518147 · HTR2C Gene · Chr X · Antipsychotic Side Effects
Polymorphisms of the HTR2C gene and antipsychotic-induced weight gain: an update and meta-analysis.
Association of the HTR2C gene and antipsychotic induced weight gain: a meta-analysis.
Content updated August 2026.
ReadYourDNA provides educational interpretation of DNA data you already have. It is not diagnostic, not a substitute for professional medical advice, diagnosis, or treatment, and is not intended to diagnose, treat, cure, or prevent any disease. Talk to a clinician before acting on any result.
Raw DNA Data Reports for 23andMe & AncestryDNA · About ReadYourDNA · FAQ · Methodology & Science · Pricing · Support and complaints · Legal & Contact · Health Traits · Pharmacogenomics · Carrier Status · Variant Explorer · The Human Karyotype · Privacy Policy · Terms of Service · Accessibility · Consumer Health Data Privacy · Your Privacy Choices · Editorial Standards · Your Data, Checkable · Sample Report · ReadYourDNA and Promethease compared · What is inside a 23andMe raw data file · What is inside an AncestryDNA raw data file · What a chatbot can and cannot do with your raw DNA file · Where a raw DNA file can still be uploaded in 2026
Written, maintained and operated by Martin Pechhacker, sole proprietor, Vienna, Austria. Trade register GISA 40064420. support@readyourdna.com