What you carry at this position in your DNA and what research says about it.
Blood Sugar Regulation: 9/10 evidence, 25 publications.
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Sample genotype (not yours): C/C
Typical Blood Sugar and Lower Diabetes Risk
Carrying two copies of the common C allele is associated with optimal insulin secretion and standard fasting glucose levels. This genetic profile helps maintain healthy metabolic function and a lower baseline risk for type 2 diabetes.
What this genotype means: Typical fasting blood sugar levels; Lower baseline risk of type 2 diabetes; Reduced susceptibility to gestational diabetes.
Sample genotype (not yours): C/T
Slightly Elevated Blood Sugar and Diabetes Risk
Carrying one copy of the T allele is linked to a modest increase in fasting blood glucose and a slightly higher risk of type 2 diabetes. This profile can lead to slightly reduced insulin secretion in response to sugar intake.
What this genotype means: Slightly higher fasting glucose levels; Modestly increased risk of type 2 diabetes; Elevated risk of gestational diabetes during pregnancy.
Sample genotype (not yours): T/T
Higher Blood Sugar and Elevated Diabetes Risk
Carrying two copies of the T allele is associated with elevated fasting glucose levels and a higher risk of metabolic challenges. This genetic profile can noticeably reduce insulin secretion, particularly during fasting or pregnancy.
What this genotype means: Elevated fasting blood sugar levels; Increased risk of developing type 2 diabetes; Higher susceptibility to gestational diabetes.
Gene function and biological role
Gene Function: The MTNR1B gene encodes the melatonin receptor 1B, a specialized protein that binds the hormone melatonin to coordinate circadian rhythms and metabolic processes [1]. Melatonin is widely known for regulating sleep, but it also plays a critical role in controlling insulin release from pancreatic beta cells [1]. By modulating how these cells respond to melatonin, the gene helps maintain stable blood glucose levels throughout the day and night [2]. Variations in this gene can alter receptor expression, directly impacting how efficiently the body processes sugar [2].
Variant Impact: The rs1387153 variant is an intergenic single nucleotide polymorphism located near the MTNR1B gene on chromosome 11. This genetic change influences the expression of melatonin receptors in pancreatic tissue, which can disrupt normal insulin secretion in response to glucose [3]. The T allele is associated with higher fasting blood sugar levels and a reduced early insulin response [1]. Over time, this altered signaling can increase susceptibility to metabolic challenges, particularly during periods of physiological stress like pregnancy [1].
Key Insight: Your sleep hormone, melatonin, directly influences how your pancreas releases insulin, linking your circadian rhythm to your blood sugar levels.
Location: MTNR1B. Chromosome 11 · 11q14.3 · 92.9 Mb
Estimated prevalence by population
Global 46.9%; European 50.3%; African 41.4%; East Asian 30.9%; South Asian 37.2%; Americas 58.5%; Ashkenazi 52.2%; Finnish 41.7%; Middle Eastern 47.7%; Amish 25.4%.
Estimated CC genotype frequency.
Global 42.8%; European 41.3%; African 45.9%; East Asian 49.4%; South Asian 47.6%; Americas 35.9%; Ashkenazi 40.1%; Finnish 45.8%; Middle Eastern 42.7%; Amish 50.0%.
Estimated CT genotype frequency.
Global 10.3%; European 8.5%; African 12.7%; East Asian 19.7%; South Asian 15.2%; Americas 5.5%; Ashkenazi 7.7%; Finnish 12.6%; Middle Eastern 9.6%; Amish 24.6%.
Estimated TT genotype frequency.
Showing effects for C/C genotype
Cardiovascular & Metabolic
Diabetes & Glycemic Traits
Fasting Glucose. Evidence: 6/10. Source: PMID 19060909. Typical.
Type 2 Diabetes. Evidence: 6/10. Source: PMID 20581827. Typical Risk.
HbA1c. Evidence: 9/10. Source: PMID 20858683. Typical.
Metabolic Syndrome & Insulin Resistance
Metabolic Syndrome. Evidence: 5/10. Source: PMID 21386085. Typical Risk.
Hypertension
Pulse Pressure. Evidence: 6/10. Source: PMID 33230300. Typical.
Endocrine & Reproductive
Pregnancy & Birth Complications
Gestational Diabetes. Evidence: 4/10. Source: PMID 26563312. Lower Risk.
Showing effects for C/T genotype
Fasting Glucose. Evidence: 6/10. Source: PMID 19060909. +0.07 mmol/L.
Type 2 Diabetes. Evidence: 6/10. Source: PMID 20581827. ~1.09x Risk.
HbA1c. Evidence: 9/10. Source: PMID 20858683. +0.03%.
Metabolic Syndrome. Evidence: 5/10. Source: PMID 21386085. Slightly Increased.
Pulse Pressure. Evidence: 6/10. Source: PMID 33230300. +0.11 mmHg.
Gestational Diabetes. Evidence: 4/10. Source: PMID 26563312. Increased Risk.
Showing effects for T/T genotype
Fasting Glucose. Evidence: 6/10. Source: PMID 19060909. +0.14 mmol/L.
Type 2 Diabetes. Evidence: 6/10. Source: PMID 20581827. ~1.18x Risk.
HbA1c. Evidence: 9/10. Source: PMID 20858683. +0.06%.
Metabolic Syndrome. Evidence: 5/10. Source: PMID 21386085. Increased Risk.
Pulse Pressure. Evidence: 6/10. Source: PMID 33230300. +0.22 mmHg.
Gestational Diabetes. Evidence: 4/10. Source: PMID 26563312. Higher Risk.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Maintaining balanced blood sugar levels is more efficient with this genotype, as it supports typical melatonin receptor activity in the pancreas [1]. Research indicates that having two copies of the C allele correlates with lower fasting plasma glucose and standard HbA1c levels [2]. Pancreatic beta cells can release insulin effectively in response to glucose, reducing the likelihood of insulin resistance [3]. Consequently, the risk of developing type 2 diabetes or metabolic syndrome is not elevated by this genetic marker [4]. Pregnant individuals with this profile also experience a lower risk of gestational diabetes [5].
Typical fasting blood sugar levels; Lower baseline risk of type 2 diabetes; Reduced susceptibility to gestational diabetes.
Sample genotype: CT (Heterozygous)
Processing dietary sugars may be slightly less efficient due to altered melatonin receptor expression in the pancreas [1]. Studies show that carrying one T allele is associated with a minor increase in fasting plasma glucose and HbA1c levels [2]. This change can slightly impair the early phase of insulin release after eating, leading to mild insulin resistance [3]. The risk of developing type 2 diabetes is elevated by approximately 9% compared to the typical genotype [4]. During pregnancy, this genetic variation is also associated with a moderately higher susceptibility to gestational diabetes [5].
Slightly higher fasting glucose levels; Modestly increased risk of type 2 diabetes; Elevated risk of gestational diabetes during pregnancy.
Sample genotype: TT (Homozygous)
Pancreatic beta cells may exhibit altered sensitivity to melatonin, which suppresses insulin release and raises fasting blood sugar [1]. Clinical data links this genotype to higher average fasting glucose and elevated HbA1c levels [2]. The body's ability to secrete insulin promptly after a meal is often reduced, contributing to insulin resistance [3]. These metabolic changes result in a higher risk of developing type 2 diabetes and metabolic syndrome [4]. Pregnant women with this genotype have a significantly increased risk of developing gestational diabetes [5].
Elevated fasting blood sugar levels; Increased risk of developing type 2 diabetes; Higher susceptibility to gestational diabetes.
Variants with shared genetic architecture
rs10830963 · MTNR1B Gene · Chr 11 · Type 2 Diabetes Risk
rs10830962 · MTNR1B Gene · Chr 11 · Gestational Diabetes Risk
rs4753426 · MTNR1B Gene · Chr 11 · Diabetes Risk
Variants in MTNR1B influence fasting glucose levels.
Twelve type 2 diabetes susceptibility loci identified through large-scale association analysis.
Content updated August 2026.
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