What you carry at this position in your DNA and what research says about it.
Gut Health and Immunity: 9/10 evidence, 24 publications.
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Sample genotype (not yours): C/C
Typical Gut and Inflammatory Risk
This genotype represents the classic secretor status, which maintains a typical baseline risk for inflammatory gut conditions. It is associated with normal secretion of blood group antigens into mucosal linings.
What this genotype means: Typical risk of Crohn's disease; Typical cholesterol levels; Slightly higher susceptibility to severe COVID-19.
Sample genotype (not yours): C/T
Carrying one functional copy of the secretor gene is sufficient to maintain normal antigen secretion and typical inflammatory risk. It offers a balanced gut health profile.
Sample genotype (not yours): T/T
Non-Secretor Status with Mixed Health Trade-offs
This genotype results in non-secretor status, which elevates the risk of inflammatory gut conditions but offers protection against certain viral infections. It represents a classic genetic trade-off.
What this genotype means: Increased risk of Crohn's disease; Lower risk of severe COVID-19; Higher vitamin B12 levels.
Gene function and biological role
Gene Function: The FUT2 gene encodes the fucosyltransferase 2 enzyme, which plays a pivotal role in determining an individual's secretor status [1]. This enzyme is responsible for secreting ABO blood group antigens into bodily fluids and onto mucosal surfaces, such as the lining of the gastrointestinal and respiratory tracts [1]. These secreted antigens act as physical barriers and decoy receptors that interact with various microbes and pathogens [1]. Approximately twenty percent of people of European descent carry loss-of-function variants in both copies of this gene, making them non-secretors [2]. Non-secretor status significantly alters the composition of the gut microbiome and influences susceptibility to several infectious and inflammatory diseases [2].
Variant Impact: The rs516246 variant is an intronic single nucleotide polymorphism in the FUT2 gene that is in near-perfect linkage disequilibrium with the primary nonsense mutation determining secretor status [3]. The C allele represents the functional secretor lineage, whereas the T allele is strongly linked to the non-functional, non-secretor lineage [3]. This genetic change directly influences the presence of blood group antigens in mucosal secretions, thereby altering host-pathogen interactions [3]. It is widely studied for its pleiotropic effects on inflammatory bowel disease, lipid metabolism, and viral susceptibility [2].
Key Insight: Being a non-secretor protects against certain highly contagious stomach flu viruses like norovirus, but it simultaneously increases the risk of chronic inflammatory conditions like Crohn's disease.
Location: FUT2. Chromosome 19 · 19q13.33 · 48.7 Mb
Estimated prevalence by population
Global 32.3%; European 27.3%; African 25.3%; East Asian 99.3%; South Asian 49.7%; Americas 40.0%; Ashkenazi 30.9%; Finnish 40.0%; Middle Eastern 19.6%; Amish 42.3%.
Estimated CC genotype frequency.
Global 47.3%; European 49.9%; African 50.0%; East Asian 0.7%; South Asian 41.6%; Americas 46.5%; Ashkenazi 49.4%; Finnish 46.5%; Middle Eastern 49.3%; Amish 45.5%.
Estimated CT genotype frequency.
Global 20.4%; European 22.8%; African 24.7%; East Asian < 0.1%; South Asian 8.7%; Americas 13.5%; Ashkenazi 19.7%; Finnish 13.5%; Middle Eastern 31.1%; Amish 12.2%.
Estimated TT genotype frequency.
Showing effects for C/C genotype
Immunity & Inflammation
Chronic Inflammatory Diseases
Crohn's Disease. Evidence: 7/10. Source: PMID 23128233. Typical Risk.
Infection Susceptibility & Resistance
COVID-19 Severity. Evidence: 6/10. Source: PMID 37198478. ~1.11x Higher Risk.
Organ Systems
Digestive & Gut Disorders
Peptic Ulcer. Evidence: 8/10. Source: PMID 38102678. Typical Risk.
Nutrition & Metabolism
Vitamin & Mineral Metabolism
Vitamin B12 Levels. Evidence: 3/10. Source: PMID 23251661. Typical Levels.
Cardiovascular & Metabolic
Lipids & Cholesterol
LDL Cholesterol. Evidence: 9/10. Source: PMID 29507422. Typical Levels.
Showing effects for C/T genotype
Showing effects for T/T genotype
Crohn's Disease. Evidence: 7/10. Source: PMID 23128233. ~1.12x Higher Risk.
COVID-19 Severity. Evidence: 6/10. Source: PMID 37198478. Lower Risk.
Peptic Ulcer. Evidence: 8/10. Source: PMID 38102678. Increased Risk.
Vitamin B12 Levels. Evidence: 3/10. Source: PMID 23251661. Higher Levels.
LDL Cholesterol. Evidence: 9/10. Source: PMID 29507422. Higher Levels.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Having two copies of the C allele ensures fully functional FUT2 enzyme activity, allowing the secretion of ABO blood group antigens into saliva and mucosal linings [1]. This secretor status is associated with a typical, lower risk of developing Crohn's disease and peptic ulcers compared to non-secretors [1]. However, the presence of these mucosal antigens provides binding sites for certain pathogens, slightly increasing susceptibility to severe respiratory infections like COVID-19 [2]. Lipid profiles generally remain within typical ranges, with lower baseline LDL and total cholesterol levels compared to those with the T/T genotype [3]. Vitamin B12 levels also tend to be typical rather than elevated [4]. Overall, this genotype represents the evolutionary baseline for human mucosal immunity.
Typical risk of Crohn's disease; Typical cholesterol levels; Slightly higher susceptibility to severe COVID-19.
Sample genotype: CT (Heterozygous)
Possessing one functional C allele and one non-functional T allele results in a secretor phenotype, as secretor status is genetically dominant [1]. The body continues to produce and secrete ABO blood group antigens onto mucosal surfaces, protecting against chronic inflammatory gut conditions [1]. Consequently, risks for Crohn's disease and peptic ulcers remain at typical baseline levels [1]. Similar to the C/C genotype, the presence of mucosal antigens means typical susceptibility to certain viral pathogens, including a slightly higher risk of severe COVID-19 compared to non-secretors [2]. Cholesterol levels and vitamin B12 levels generally align with typical population averages [3]. This heterozygous state provides a stable, standard physiological profile.
Sample genotype: TT (Homozygous)
Carrying two copies of the T allele leads to a complete lack of functional FUT2 enzyme activity, resulting in non-secretor status where ABO blood group antigens are absent from bodily fluids [1]. This absence alters the gut microbiome and is linked to an increased risk of Crohn's disease and peptic ulcers [1]. On the positive side, many common pathogens require these mucosal antigens to infect host cells; consequently, non-secretors enjoy strong resistance to norovirus and a lower risk of severe COVID-19 [2]. This genotype is also associated with higher circulating levels of vitamin B12 [3]. However, it may also lead to slightly elevated LDL and total cholesterol levels [4]. Managing gut health and monitoring lipid levels are useful considerations for individuals with this profile.
Increased risk of Crohn's disease; Lower risk of severe COVID-19; Higher vitamin B12 levels; Slightly higher LDL cholesterol.
Variants with shared genetic architecture
rs602662 · FUT2 Gene · Chr 19 · Vitamin B12 and Gut Health
rs1047781 · FUT2 Gene · Chr 19 · Norovirus and Gut Health
rs492602 · FUT2 Gene · Chr 19 · Cholesterol and Gut Health
Host-microbe interactions have shaped the genetic architecture of inflammatory bowel disease.
GWAS and meta-analysis identifies 49 genetic variants underlying critical COVID-19.
A large electronic-health-record-based genome-wide study of serum lipids.
Content updated August 2026.
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