SLC22A1 rs1050152: Understanding the OCT1 Met420del Variant
The rs1050152 variant in the SLC22A1 gene, often referred to as the OCT1 Met420del mutation, involves a deletion that affects the function of a key liver transporter. This genetic change is associated with reduced hepatic uptake of metformin, which may influence how individuals with type 2 diabetes respond to the medication.
What each genotype means
Normal OCT1 transporter activity
This genotype represents the wild-type or reference sequence for the SLC22A1 gene at this position. Individuals with this profile possess the standard functional version of the OCT1 transporter, which is responsible for the hepatic uptake of metformin. Please discuss your medication response and any concerns regarding glycemic control with your healthcare provider or pharmacist.
This is the most common genotype in most global populations, though frequency varies significantly by ancestry.
Reduced OCT1 transporter activity
This genotype includes one copy of the deletion variant (often referred to as p.Met420del), which may lead to reduced function of the OCT1 transporter protein. Research suggests that carriers of this variant may experience diminished hepatic uptake of metformin, potentially impacting its glycemic response. Please consult your clinician or pharmacist to discuss how this may relate to your specific treatment plan.
The deletion allele is carried by roughly 1 in 6 people of European ancestry, making this heterozygous genotype relatively common in those populations.
Significantly reduced transporter activity
This genotype indicates the presence of two copies of the deletion variant, which is associated with a loss-of-function in the OCT1 transporter. Studies suggest this may lead to a more pronounced reduction in the hepatic uptake of metformin compared to non-carriers, potentially affecting how well the medication lowers blood glucose levels. Because evidence regarding clinical outcomes remains limited and mixed, you should discuss your metformin dosing and glycemic response with your healthcare provider.
This homozygous genotype is less common than the heterozygous form, occurring in a smaller percentage of individuals within European cohorts.
What is rs1050152?
The variant rs1050152 is a specific genetic alteration located within the SLC22A1 gene, which resides on chromosome 6. In scientific literature, this variant is frequently identified as the Met420del mutation, representing a deletion of a methionine amino acid at position 420 of the resulting protein. Because this change occurs within the coding region of the gene, it directly alters the structure of the protein it encodes. Geneticists categorize this as a loss-of-function variant because the deletion impairs the normal activity of the protein. Understanding such variants is a primary focus of pharmacogenomics, a field that studies how an individual's genetic makeup influences their response to drugs. By identifying these specific changes, researchers aim to better understand why patients may experience different therapeutic outcomes when prescribed the same medication.
The Role of the SLC22A1 Gene
The SLC22A1 gene provides instructions for creating the Organic Cation Transporter 1 (OCT1) protein. This protein acts as a molecular gatekeeper, primarily expressed in the liver, where it facilitates the transport of various substances, including medications, into cells. For the diabetes drug metformin, OCT1 is essential; it allows the drug to enter hepatocytes, the main functional cells of the liver. Once inside, metformin exerts its glucose-lowering effects by inhibiting gluconeogenesis and improving insulin sensitivity. When the SLC22A1 gene carries the rs1050152 deletion, the resulting OCT1 protein may have a diminished capacity to transport metformin effectively. Consequently, less of the drug reaches its target site within the liver, which can theoretically lead to variations in how well the medication manages blood glucose levels in patients with type 2 diabetes.
Research and Evidence Strength
Research into rs1050152 has primarily focused on its impact on metformin efficacy. Studies have observed that individuals carrying this variant may exhibit reduced glycemic responses to metformin compared to those without the deletion. While some clinical studies have demonstrated a clear link between this variant and altered drug transport, the overall evidence strength is currently considered limited. This is because clinical outcomes are complex and influenced by many factors, including diet, lifestyle, other medications, and additional genetic variants in other transporter genes like SLC47A1 or SLC22A2. Furthermore, findings have been mixed across different ethnic populations, suggesting that the impact of this variant may not be universal. Because of these variables, the scientific community continues to investigate how much this specific variant contributes to the overall variability in patient response to metformin therapy.
Population Frequency
The prevalence of the rs1050152 variant varies significantly across different global populations. In European cohorts, the deletion allele is relatively common, with a frequency typically reported between 0.15 and 0.20. This means that a notable portion of the population carries at least one copy of this variant. However, frequency data can differ substantially when looking at other ancestral groups, highlighting the importance of considering genetic diversity in pharmacogenomic research. Because this variant is relatively common in certain groups, it has been the subject of extensive study regarding its potential role in personalized medicine. Researchers use these frequency statistics to design better clinical trials and to understand the distribution of genetic traits that might influence drug metabolism on a global scale.
Navigating Your Genetic Information
If you are aware that you carry the rs1050152 variant, it is important to understand that this information does not serve as a medical diagnosis or a definitive predictor of how you will respond to any medication. Pharmacogenomics is a developing field, and genetic markers are only one piece of a much larger puzzle that includes your overall health, medical history, and other environmental factors. You should never use genetic information to make changes to your prescribed treatment plan, such as altering your dosage or stopping a medication, without first consulting your healthcare provider. Your doctor or pharmacist is the best resource for interpreting how your genetic profile might relate to your specific clinical situation. They can provide guidance based on established clinical guidelines and your unique health needs, ensuring that any decisions regarding your therapy are safe and evidence-based.
How common is this variant?
The deletion allele associated with rs1050152 is found at a frequency of approximately 0.15 to 0.20 in European populations. Frequency data varies across other global ancestries, reflecting the diverse genetic landscape of the SLC22A1 gene.
Frequently asked questions
Does having the rs1050152 variant mean metformin won't work for me?
No, having this variant does not mean the medication will not work. It is associated with a potential reduction in drug uptake, but many factors influence how well metformin controls blood sugar, and many patients with this variant still achieve successful treatment outcomes.
Should I get tested for the SLC22A1 variant before starting metformin?
Routine genetic testing for this variant is not currently a standard clinical requirement before starting metformin. Decisions about your treatment should be based on clinical guidelines and discussions with your healthcare provider regarding your specific health needs.
Can I change my metformin dose based on my genotype?
You should never change your medication dosage based on genetic test results without consulting your doctor. Only a qualified healthcare professional can determine if a dosage adjustment is appropriate based on your clinical response and overall health profile.
Is rs1050152 the only gene that affects metformin response?
No, metformin response is complex and influenced by multiple genes, including other transporters like SLC47A1 and SLC22A2. Genetic variation is just one of many factors, including lifestyle and diet, that contribute to how an individual responds to the drug.
Sources & further reading
Educational information only, last refreshed 9/21/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Functional non-synonymous variant (M420del) in the organic cation transporter OCT1, significantly impacting the hepatic uptake of various drugs including metformin.
An intronic variant in the organic cation transporter gene associated with altered metformin side-effect profiles.
A variant associated with the occurrence of gastrointestinal side effects in metformin users.
Variant in SLC22A1 (OCT1) associated with altered metformin transport and glycemic response.
A missense variant in OCT1 that impairs organic cation cellular uptake, altering clinical responsiveness and gastrointestinal tolerance to metformin.
A well-characterized loss-of-function variant (M420del) in the organic cation transporter 1 (OCT1) that reduces hepatic uptake of metformin and other basic drugs, modulating therapeutic efficacy and side effects.