What you carry at this position in your DNA and what research says about it.
Fetal Hemoglobin Levels: 9/10 evidence, 16 publications.
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Sample genotype (not yours): G/G
Typical Fetal Hemoglobin and Blood Cell Levels
This genotype is associated with typical levels of fetal hemoglobin and standard blood cell characteristics. It represents the most common genetic baseline globally.
What this genotype means: Typical fetal hemoglobin levels; Standard blood pressure baseline; Typical platelet and red blood cell counts.
Sample genotype (not yours): A/A
Highest Fetal Hemoglobin and Most Favorable Blood Profile
Carrying two copies of the A allele is linked to the highest levels of fetal hemoglobin. It also correlates with the lowest diastolic blood pressure and LDL cholesterol.
What this genotype means: Highest fetal hemoglobin levels; Lowest diastolic blood pressure; Lowest LDL cholesterol.
Sample genotype (not yours): G/A
Slightly Higher Fetal Hemoglobin and Favorable Blood Profile
Carrying one copy of the A allele is linked to slightly higher fetal hemoglobin levels. It is also associated with slightly lower blood pressure and LDL cholesterol.
What this genotype means: Slightly higher fetal hemoglobin; Slightly lower diastolic blood pressure; Slightly lower LDL cholesterol.
Gene function and biological role
Gene Function: The HBS1L-MYB intergenic region is a major modifier of fetal hemoglobin levels in adults [1]. This region contains regulatory elements that control the expression of the MYB gene, which is a key transcription factor in red blood cell development [2]. Changes in this region alter transcription factor binding and long-range chromatin interactions with the MYB promoter [1]. Consequently, these genetic variations influence several red blood cell characteristics and platelet counts [3]. In patients with sickle cell disease or beta-thalassemia, these variations can significantly alter clinical severity [1].
Variant Impact: The rs9402686 variant is located in the HBS1L-MYB intergenic region on chromosome 6. The minor A allele of this variant is strongly associated with increased levels of fetal hemoglobin [1]. This genetic change is thought to reduce the binding of specific transcription factors, leading to downstream alterations in erythropoiesis [1]. Beyond fetal hemoglobin, this variant is linked to variations in platelet count and red blood cell size [3]. It also shows associations with systemic traits like diastolic blood pressure and LDL cholesterol levels [4].
Key Insight: The minor A allele of this variant acts as a natural booster of fetal hemoglobin, which helps protect against complications in blood disorders like sickle cell anemia.
Location: HBS1L. Chromosome 6 · 6q23.3 · 135.1 Mb
Estimated prevalence by population
Global 64.0%; European 53.6%; African 86.1%; East Asian 51.9%; South Asian 79.2%; Americas 65.1%; Ashkenazi 58.1%; Finnish 42.4%; Middle Eastern 63.9%; Amish 65.6%.
Estimated GG genotype frequency.
Global 31.0%; European 39.2%; African 13.3%; East Asian 40.3%; South Asian 19.6%; Americas 31.1%; Ashkenazi 36.3%; Finnish 45.4%; Middle Eastern 32.1%; Amish 30.8%.
Estimated GA genotype frequency.
Global 5.1%; European 7.2%; African 0.5%; East Asian 7.8%; South Asian 1.2%; Americas 3.7%; Ashkenazi 5.7%; Finnish 12.2%; Middle Eastern 4.0%; Amish 3.6%.
Estimated AA genotype frequency.
Showing effects for G/G genotype
Rare Genetic Disorders
Hemoglobinopathies
Fetal Hemoglobin. Evidence: 4/10. Source: PMID 19148297. Typical Levels.
Cardiovascular & Metabolic
Hypertension
Diastolic Blood Pressure. Evidence: 6/10. Source: PMID 33230300. Typical Baseline.
Lipids & Cholesterol
LDL Cholesterol. Evidence: 8/10. Source: PMID 39024449. Typical Baseline.
Blood Cell & Iron Traits
Red Cell Distribution Width. Evidence: 8/10. Source: PMID 39024449. Typical Baseline.
Platelet Count. Evidence: 9/10. Source: PMID 34553764. Typical Baseline.
Red Blood Cell Size. Evidence: 9/10. Source: PMID 19820697. Typical Baseline.
Iron Levels. Evidence: 8/10. Source: PMID 39024449. Typical Baseline.
Showing effects for A/A genotype
Fetal Hemoglobin. Evidence: 4/10. Source: PMID 19148297. Highest Levels.
Diastolic Blood Pressure. Evidence: 6/10. Source: PMID 33230300. Lowest Baseline.
LDL Cholesterol. Evidence: 8/10. Source: PMID 39024449. Lowest Baseline.
Red Cell Distribution Width. Evidence: 8/10. Source: PMID 39024449. Lowest Baseline.
Platelet Count. Evidence: 9/10. Source: PMID 34553764. Highest Baseline.
Red Blood Cell Size. Evidence: 9/10. Source: PMID 19820697. Highest Baseline.
Iron Levels. Evidence: 8/10. Source: PMID 39024449. Highest Baseline.
Showing effects for G/A genotype
Fetal Hemoglobin. Evidence: 4/10. Source: PMID 19148297. Slightly Higher.
Diastolic Blood Pressure. Evidence: 6/10. Source: PMID 33230300. Slightly Lower.
LDL Cholesterol. Evidence: 8/10. Source: PMID 39024449. Slightly Lower.
Red Cell Distribution Width. Evidence: 8/10. Source: PMID 39024449. Slightly Lower.
Platelet Count. Evidence: 9/10. Source: PMID 34553764. Slightly Higher.
Red Blood Cell Size. Evidence: 9/10. Source: PMID 19820697. Slightly Higher.
Iron Levels. Evidence: 8/10. Source: PMID 39024449. Slightly Higher.
What this genotype means for the people who carry it
Sample genotype: GG (Homozygous)
Having the G/G genotype means carrying two copies of the major G allele, which represents the standard baseline across most global populations. This genotype is associated with typical, low levels of fetal hemoglobin in adulthood, which is normal and healthy [1]. However, in individuals with blood disorders like sickle cell disease, this baseline level does not provide the protective buffering effect seen with the minor allele [2]. Additionally, this genotype is linked to typical baselines for diastolic blood pressure and LDL cholesterol [3]. It also correlates with standard red blood cell size and typical platelet counts [4]. These standard hematological parameters mean that your body maintains typical oxygen transport and blood clotting dynamics [4]. There are no elevated cardiovascular or hematological risks directly attributed to this genotype, as it simply represents the common human baseline [3]. Overall, this genetic profile is considered neutral and typical for the general population [1].
Typical fetal hemoglobin levels; Standard blood pressure baseline; Typical platelet and red blood cell counts.
Sample genotype: AA (Homozygous)
Carrying two copies of the minor A allele is strongly associated with the highest levels of adult fetal hemoglobin [1]. This elevated fetal hemoglobin acts as a natural protective factor, particularly beneficial for individuals with hemoglobin disorders like sickle cell anemia [2]. This genotype is also associated with the lowest diastolic blood pressure and the lowest LDL cholesterol levels within this variant's spectrum [3]. Additionally, it correlates with the highest platelet counts and larger red blood cell sizes (mean corpuscular volume) [4]. These hematological variations are typically benign and represent a highly favorable cardiovascular and blood profile [3] [4]. The increased fetal hemoglobin can enhance oxygen transport efficiency under low-oxygen conditions [2]. It also reflects a unique genetic variation that influences how your bone marrow produces and matures red blood cells [4]. Overall, this genotype provides subtle but positive cardiovascular and hematological advantages [3].
Highest fetal hemoglobin levels; Lowest diastolic blood pressure; Lowest LDL cholesterol.
Sample genotype: GA (Heterozygous)
Carrying one copy of the minor A allele is associated with a slight increase in adult fetal hemoglobin levels [1]. In individuals with sickle cell disease or beta-thalassemia, even a modest increase in fetal hemoglobin can help reduce the severity of symptoms [2]. This genotype is also linked to slightly lower diastolic blood pressure and reduced LDL cholesterol levels compared to the typical baseline [3]. Furthermore, it is associated with a slight increase in platelet count and mean corpuscular volume [4]. These subtle shifts in blood cell characteristics are generally benign and fall within normal healthy ranges [4]. The presence of the A allele suggests a slightly more efficient oxygen-carrying capacity under certain physiological stresses [2]. It also contributes to a marginally more favorable cardiovascular profile over time [3]. Most individuals with this genotype will experience typical health outcomes with no noticeable symptoms [1].
Slightly higher fetal hemoglobin; Slightly lower diastolic blood pressure; Slightly lower LDL cholesterol.
Variants with shared genetic architecture
rs9376090 · HBS1L Gene · Chr 6 · Blood and Heart Health
rs7775698 · HBS1L Gene · Chr 6 · Fetal Hemoglobin Levels
rs35786788 · HBS1L Gene · Chr 6 · Red Blood Cell Health
Sickle Cell Disease in the Post Genomic Era: A Monogenic Disease with a Polygenic Phenotype.
Diversity and scale: Genetic architecture of 2068 traits in the VA Million Veteran Program.
Content updated August 2026.
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