What you carry at this position in your DNA and what research says about it.
Type 2 Diabetes Risk: 10/10 evidence, 81 publications.
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Sample genotype (not yours): C/C
Higher Risk of Type 2 Diabetes
Two copies of the C allele are linked to reduced insulin secretion and higher blood sugar levels. This combination increases the long-term risk of developing type 2 diabetes.
What this genotype means: Reduced first-phase insulin secretion; Higher average blood glucose and HbA1c; Increased susceptibility to type 2 diabetes.
Sample genotype (not yours): C/T
Moderately Increased Risk of Type 2 Diabetes
A single copy of the C allele is associated with slightly lower insulin secretion efficiency. This moderately increases the risk of elevated blood sugar and type 2 diabetes.
What this genotype means: Slightly reduced insulin secretion capacity; Slightly elevated blood sugar markers; Moderate increase in type 2 diabetes risk.
Sample genotype (not yours): T/T
Typical Risk of Type 2 Diabetes
Two copies of the T allele provide optimal zinc transport in pancreatic cells, supporting efficient insulin storage. This genotype is associated with a lower risk of type 2 diabetes and healthier blood sugar levels.
What this genotype means: Efficient insulin storage and secretion; Lower average blood glucose and HbA1c; Reduced risk of type 2 diabetes.
Gene function and biological role
Gene Function: The SLC30A8 gene encodes zinc transporter 8 (ZnT8), a protein highly concentrated in the insulin-producing beta-cells of the pancreas [1]. This transporter is responsible for moving zinc ions into secretory vesicles, where zinc is essential for crystallizing and storing insulin [1]. Proper zinc transport is crucial for maintaining stable insulin structures and regulating its release into the bloodstream [2]. Genetic variations in this gene can alter the transporter's efficiency, directly impacting how the body manages blood sugar [3]. Consequently, SLC30A8 is one of the most heavily studied genes in the genetics of metabolic health and diabetes risk [4].
Variant Impact: The rs13266634 variant is a missense mutation in the SLC30A8 gene that changes the amino acid at position 325 from arginine to tryptophan [5]. This specific change, often written as p.Arg325Trp or R325W, alters the structure of the ZnT8 transporter's C-terminal domain [6]. The arginine-encoding C allele is the more common version globally and is associated with reduced insulin secretion [3]. In contrast, the tryptophan-encoding T allele produces a more stable transporter structure that may optimize insulin release [1]. This single letter change represents one of the most robustly replicated genetic risk factors for type 2 diabetes across diverse human populations [4].
Key Insight: Rare variants that completely disable this zinc transporter actually protect against diabetes, which inspired researchers to develop new drugs that mimic this protective effect.
Location: SLC30A8. Chromosome 8 · 8q24.11 · 117.2 Mb
Estimated prevalence by population
Global 57.7%; European 48.4%; African 82.4%; East Asian 30.2%; South Asian 59.0%; Americas 56.3%; Ashkenazi 54.3%; Finnish 36.0%; Middle Eastern 58.6%; Amish 69.2%.
Estimated CC genotype frequency.
Global 35.0%; European 42.4%; African 16.7%; East Asian 49.5%; South Asian 35.6%; Americas 37.4%; Ashkenazi 38.7%; Finnish 48.0%; Middle Eastern 35.9%; Amish 28.0%.
Estimated CT genotype frequency.
Global 7.3%; European 9.3%; African 0.9%; East Asian 20.3%; South Asian 5.4%; Americas 6.2%; Ashkenazi 6.9%; Finnish 16.0%; Middle Eastern 5.5%; Amish 2.8%.
Estimated TT genotype frequency.
Showing effects for C/C genotype
Cardiovascular & Metabolic
Diabetes & Glycemic Traits
Type 2 Diabetes. Evidence: 10/10. Source: PMID 17293876. ~1.12x Higher Risk.
Blood Glucose. Evidence: 10/10. Source: PMID 25625282. Higher Levels.
HbA1c. Evidence: 10/10. Source: PMID 19096518. Higher Levels.
Diabetic Complications. Evidence: 8/10. Source: PMID 39024449. Increased Risk.
Lipids & Cholesterol
Triglycerides. Evidence: 10/10. Source: PMID 17463246. Higher Levels.
Showing effects for C/T genotype
Type 2 Diabetes. Evidence: 10/10. Source: PMID 17293876. Increased Risk.
Blood Glucose. Evidence: 10/10. Source: PMID 25625282. Slightly Higher.
HbA1c. Evidence: 10/10. Source: PMID 19096518. Slightly Higher.
Diabetic Complications. Evidence: 8/10. Source: PMID 39024449. Slightly Increased.
Triglycerides. Evidence: 10/10. Source: PMID 17463246. Slightly Higher.
Showing effects for T/T genotype
Type 2 Diabetes. Evidence: 10/10. Source: PMID 17293876. Typical Risk.
Blood Glucose. Evidence: 10/10. Source: PMID 25625282. Typical Levels.
HbA1c. Evidence: 10/10. Source: PMID 19096518. Typical Levels.
Diabetic Complications. Evidence: 8/10. Source: PMID 39024449. Typical Risk.
Triglycerides. Evidence: 10/10. Source: PMID 17463246. Typical Levels.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Inheriting the C allele from both parents means the pancreatic beta-cells produce a version of the ZnT8 transporter that contains arginine [1]. This version is associated with a 19% reduction in first-phase insulin release following a glucose load [2]. Over time, the reduced capacity to secrete insulin under glucose stress leads to higher fasting glucose and HbA1c levels [3]. Large-scale genome-wide studies consistently link this genotype to an increased risk of type 2 diabetes [4]. Additionally, this genotype is associated with slightly elevated triglyceride levels and a higher risk of diabetic complications like retinopathy [5]. Managing dietary sugar intake and maintaining physical activity are highly effective ways to offset this genetic predisposition.
Reduced first-phase insulin secretion; Higher average blood glucose and HbA1c; Increased susceptibility to type 2 diabetes.
Sample genotype: CT (Heterozygous)
Possessing one copy of each allele means the body produces both the arginine and tryptophan versions of the ZnT8 transporter [1]. This intermediate state typically results in a moderate reduction in insulin secretion capacity compared to the protective TT genotype [2]. While the risk is lower than in those with two C alleles, carriers still show a statistically significant increase in susceptibility to type 2 diabetes [3]. Blood sugar markers like HbA1c and fasting glucose may trend slightly higher than baseline [4]. Interestingly, some studies suggest that carriers of this genotype may respond well to zinc supplementation or specific diabetes medications like repaglinide [5]. Emphasizing a balanced diet rich in whole foods helps support healthy pancreatic function.
Slightly reduced insulin secretion capacity; Slightly elevated blood sugar markers; Moderate increase in type 2 diabetes risk.
Sample genotype: TT (Homozygous)
Inheriting the T allele from both parents means all ZnT8 transporters contain tryptophan at position 325 [1]. This structural variation creates a highly stable transporter that optimizes the crystallization and storage of insulin within pancreatic beta-cells [2]. Consequently, individuals with this genotype exhibit robust insulin secretion in response to glucose loads [3]. Large genetic studies show this genotype is protective, resulting in lower average blood glucose and HbA1c levels [4]. It is also associated with lower triglyceride levels and a reduced risk of diabetic complications [5]. Maintaining a healthy lifestyle further solidifies this natural genetic advantage.
Efficient insulin storage and secretion; Lower average blood glucose and HbA1c; Reduced risk of type 2 diabetes.
Variants with shared genetic architecture
rs11558471 · SLC30A8 Gene · Chr 8 · Type 2 Diabetes Risk
rs3802177 · SLC30A8 Gene · Chr 8 · Type 2 Diabetes Risk
rs10811661 · CDKN2B Gene · Chr 9 · Type 2 Diabetes Risk
Loss of ZnT8 function protects against diabetes by enhanced insulin secretion.
A genome-wide association study identifies novel risk loci for type 2 diabetes.
Replication of genome-wide association signals in UK samples reveals risk loci for type 2 diabetes.
Differential cytolocation and functional assays of the two major human SLC30A8 (ZnT8) isoforms.
A cross-population atlas of genetic associations for 220 human phenotypes.
Diversity and scale: Genetic architecture of 2068 traits in the VA Million Veteran Program.
Content updated August 2026.
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