FMO3 Gene

What is the FMO3 gene?

FMO3 encodes flavin containing dimethylaniline monoxygenase 3, a protein involved in drug metabolism. It belongs to the Metabolism category and is part of the Pharmacogenomics biological cluster. FMO3 is the major hepatic flavin monooxygenase that oxidizes nitrogen- and sulfur-containing compounds including drugs, trimethylamine (TMA), and xenobiotics. Loss-of-function causes trimethylaminuria (fish odor syndrome).

Biological role and pathway

FMO3 is involved in the drug metabolism pathway, which plays a central role in regulating physiological processes relevant to immune defence, cellular energy, and systemic homeostasis. Genes within the Pharmacogenomics cluster work together to maintain balanced function across interconnected biological systems.

Variants in genes within this pathway may influence an individual's predisposition to altered function in these systems — particularly under conditions of physiological stress such as viral infection or prolonged illness.

Known genetic variants

The following variants (SNPs) in the FMO3 gene have been studied in relation to metabolism and chronic illness. Each variant represents a single nucleotide position where individuals may carry different alleles.

• rs2266780— FMO3 variant
• rs1736557— FMO3 variant
• rs1800822— FMO3 variant

Conditions studied in relation to FMO3

Research into FMO3 variants has explored associations with the following conditions. These are areas of scientific investigation and do not imply that FMO3 causes or treats any condition.

Genetic insights from DNA data

Consumer DNA files from 23andMe, AncestryDNA, and MyHeritage contain raw SNP data. When you upload your file to ChronicDNA, the analysis engine checks your genotype against a curated panel of 80+ genes selected for their relevance to Long COVID, ME/CFS, and connected biological pathways - some of which may include FMO3 and related genes in the pharmacogenomics pathway.

The report is educational - it explains which variants you carry, what the research says about them, and how they fit into the biological pathways most relevant to chronic illness. Results are presented in plain English with appropriate scientific context, no medical jargon, no scare tactics. All results should be discussed with a qualified healthcare provider.

Related genes in the Pharmacogenomics pathway

FMO3 does not act in isolation. The following genes are functionally related and may be analysed together for a more complete picture of your genetic predispositions.

Frequently asked questions