What you carry at this position in your DNA and what research says about it.
Type 2 Diabetes Risk: 10/10 evidence, 33 publications.
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Sample genotype (not yours): T/T
Typical Risk of Type 2 Diabetes
A pair of thymine alleles at this position represents the typical genetic baseline. Pancreatic function and insulin secretion are expected to operate normally without this specific genetic disruption.
What this genotype means: Typical insulin secretion; Baseline risk of type 2 diabetes.
Sample genotype (not yours): C/C
Higher Risk of Type 2 Diabetes
Double copies of the cytosine variant are associated with a significantly elevated risk of type 2 diabetes. Pancreatic beta cells may struggle to produce sufficient insulin, leading to higher blood sugar levels.
What this genotype means: Impaired insulin secretion and processing; Significantly increased risk of type 2 diabetes.
Sample genotype (not yours): T/C
Slightly Higher Risk of Type 2 Diabetes
Inheriting one copy of the cytosine variant is linked to a moderate increase in type 2 diabetes risk. This change can slightly reduce insulin secretion from pancreatic cells in response to glucose.
What this genotype means: Slightly reduced insulin secretion; Increased risk of type 2 diabetes.
Gene function and biological role
Gene Function: The TCF7L2 gene encodes transcription factor 7-like 2, a protein that plays a critical role in the Wnt signaling pathway [1]. This pathway is essential for the development and maintenance of pancreatic beta cells, which produce and secrete insulin [2]. Proper expression of this gene helps regulate blood glucose levels by coordinating insulin secretion in response to food intake [3]. Variations in this gene can disrupt normal insulin production and impair the body's ability to process glucose efficiently [4].
Variant Impact: The rs7901695 variant is located within an intron of the TCF7L2 gene, where it acts as a regulatory change that influences gene expression levels [1]. The change from a thymine (T) to a cytosine (C) allele is hypothesized to activate a cryptic exon or alter splicing, leading to altered transcription of the gene in pancreatic islets [5]. This molecular shift impairs insulin secretion and reduces the acute insulin response to glucose [3]. Consequently, this single nucleotide change is widely recognized as one of the strongest genetic risk factors for type 2 diabetes across diverse global populations [4].
Key Insight: Even though this variant is located in a non-coding region of the gene, it exerts a powerful effect on diabetes risk by altering how the gene is spliced and expressed in the pancreas.
Location: TCF7L2. Chromosome 10 · 10q25.2 · 113.0 Mb
Estimated prevalence by population
Global 45.3%; European 47.3%; African 29.6%; East Asian 94.8%; South Asian 48.8%; Americas 49.5%; Ashkenazi 48.0%; Finnish 61.4%; Middle Eastern 34.2%; Amish 53.0%.
Estimated TT genotype frequency.
Global 42.7%; European 42.9%; African 49.6%; East Asian 5.2%; South Asian 42.1%; Americas 41.7%; Ashkenazi 42.6%; Finnish 33.9%; Middle Eastern 48.6%; Amish 39.6%.
Estimated TC genotype frequency.
Global 12.0%; European 9.7%; African 20.8%; East Asian 0.1%; South Asian 9.1%; Americas 8.8%; Ashkenazi 9.4%; Finnish 4.7%; Middle Eastern 17.2%; Amish 7.4%.
Estimated CC genotype frequency.
Showing effects for T/T genotype
Cardiovascular & Metabolic
Diabetes & Glycemic Traits
Type 2 Diabetes. Evidence: 10/10. Source: PMID 17463249. Typical Risk.
Blood Glucose. Evidence: 6/10. Source: PMID 29403010. Typical Levels.
Heart Disease
Heart Disease. Evidence: 4/10. Source: PMID 29212778. Typical Risk.
Endocrine & Reproductive
Pregnancy & Birth Complications
Gestational Diabetes. Evidence: 3/10. Source: PMID 23456907. Typical Risk.
Showing effects for C/C genotype
Type 2 Diabetes. Evidence: 10/10. Source: PMID 17463249. ~1.7x Higher Risk.
Blood Glucose. Evidence: 6/10. Source: PMID 29403010. Elevated.
Heart Disease. Evidence: 4/10. Source: PMID 29212778. Higher Risk.
Gestational Diabetes. Evidence: 3/10. Source: PMID 23456907. Higher Risk.
Showing effects for T/C genotype
Type 2 Diabetes. Evidence: 10/10. Source: PMID 17463249. ~1.3x Higher Risk.
Blood Glucose. Evidence: 6/10. Source: PMID 29403010. Slightly Elevated.
Heart Disease. Evidence: 4/10. Source: PMID 29212778. Slightly Higher Risk.
Gestational Diabetes. Evidence: 3/10. Source: PMID 23456907. Slightly Higher Risk.
What this genotype means for the people who carry it
Sample genotype: TT (Homozygous)
Thymine alleles at this position are associated with a standard, baseline risk of developing type 2 diabetes [1]. Pancreatic beta cells in these individuals typically maintain normal insulin secretion and respond appropriately to changes in blood glucose levels [2]. Studies across multiple ethnic groups confirm that this genotype does not carry the elevated risk of impaired glucose tolerance seen in carriers of the variant allele [3]. Additionally, cardiovascular health and blood sugar markers like HbA1c generally remain within typical ranges, free from the genetic burden of this specific locus [4]. Maintaining a balanced diet and regular physical activity remains the most effective way to support metabolic health and prevent insulin resistance over time [5].
Typical insulin secretion; Baseline risk of type 2 diabetes.
Sample genotype: CC (Homozygous)
Two copies of the C variant allele are linked to a substantially increased risk of developing type 2 diabetes, with some studies showing up to a 70% higher likelihood compared to the typical genotype [1]. This homozygous state leads to a more pronounced reduction in insulin secretion and a higher proinsulin-to-insulin ratio, indicating impaired insulin processing [2]. The genetic impact is highly consistent across diverse populations, including European, African-American, and East Asian cohorts [3]. Higher average HbA1c levels and a slightly elevated risk of coronary artery disease are also associated with this genetic profile [4]. Pregnant women with this genotype face a higher risk of developing gestational diabetes [5]. Because this variant directly affects insulin production, focusing on dietary strategies that minimize rapid blood sugar spikes is highly beneficial [6].
Impaired insulin secretion and processing; Significantly increased risk of type 2 diabetes.
Sample genotype: TC (Heterozygous)
A single copy of the C variant allele is associated with an approximately 30% to 34% increase in the risk of developing type 2 diabetes [1]. This genetic change is known to impair the acute insulin response, meaning the pancreas may release less insulin immediately after a meal [2]. Research indicates that this effect is primarily driven by altered gene expression in pancreatic islets rather than insulin resistance in peripheral tissues [3]. Average blood sugar levels, as measured by HbA1c, may also be slightly higher in those with this genetic profile [4]. The risk is particularly pronounced in non-obese individuals, suggesting that genetic factors can drive diabetes independently of body weight [5]. Adopting healthy lifestyle habits, such as a low-glycemic diet and regular exercise, can significantly help offset this genetic predisposition [6].
Slightly reduced insulin secretion; Increased risk of type 2 diabetes.
Variants with shared genetic architecture
rs34872471 · TCF7L2 Gene · Chr 10 · Type 2 Diabetes Risk
rs7903146 · TCF7L2 Gene · Chr 10 · Type 2 Diabetes Risk
rs4506565 · TCF7L2 Gene · Chr 10 · Type 2 Diabetes Risk
Functional analysis of TCF7L2 genetic variants associated with type 2 diabetes.
TCF7L2 polymorphisms are associated with type 2 diabetes in northern Sweden.
Maternal genotype and gestational diabetes.
Content updated August 2026.
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