SLCO1B1: The Statin Transport Gene
Last updated: February 2026
What Is SLCO1B1?
SLCO1B1 is a gene that encodes the OATP1B1 transporter protein, located on the surface of liver cells (hepatocytes). OATP1B1 is responsible for transporting certain drugs — including statins — from the bloodstream into liver cells, where the drugs exert their cholesterol-lowering effect and are subsequently cleared.
Unlike the CYP pharmacogenes (such as the CYP2C19 gene and CYP2D6), SLCO1B1 does not encode a drug-metabolizing enzyme. It encodes a drug transporter. Reduced SLCO1B1 function does not change how fast a drug is broken down — it changes how effectively the drug reaches the liver. This distinction is important in pharmacogenomics, because the clinical consequence is higher systemic drug levels rather than altered metabolism.
SLCO1B1 and Statin Myopathy
Statins are among the most widely prescribed medications worldwide, used to lower LDL cholesterol and reduce cardiovascular risk. A well-known side effect of statins is myopathy — muscle pain, tenderness, or weakness, sometimes accompanied by elevated creatine kinase (CK) levels. In rare but serious cases, statin myopathy can progress to rhabdomyolysis.
SLCO1B1 genetic variants directly affect myopathy risk. When OATP1B1 transporter function is reduced, statins are not efficiently moved into liver cells. The result is higher statin concentrations circulating in the bloodstream, increasing exposure of muscle tissue to the drug. This is particularly relevant for simvastatin, which has the strongest evidence for SLCO1B1-related myopathy risk. The landmark SEARCH trial (Link et al., 2008; PMID: 18855540) identified rs4149056 as a major genetic determinant of simvastatin-induced myopathy.
Have 23andMe or AncestryDNA raw data? Check your SLCO1B1 status and statin myopathy risk profile.
The rs4149056 Variant
rs4149056 (c.521T>C, Val174Ala) is the most clinically significant SLCO1B1 variant. The C allele reduces OATP1B1 transporter function, leading to decreased hepatic uptake of statin substrates. This variant defines the SLCO1B1*5 allele.
The C allele frequency varies across populations: approximately 15–20% in European populations, 10–15% in South Asian populations, and 2–5% in East Asian and African populations. Approximately 1–3% of Europeans carry the CC genotype (homozygous reduced function).
SLCO1B1 Function Categories
CPIC classifies SLCO1B1 function based on the rs4149056 genotype. Learn more about how pharmacogenomic testing determines your phenotype or read our plain-language guide to metabolizer status.
- Normal Function (TT): Two reference alleles. Standard OATP1B1 transporter activity. Standard statin dosing applies.
- Intermediate Function (TC): One reference allele and one reduced-function allele. Moderately reduced hepatic statin uptake. CPIC recommends a lower simvastatin dose or an alternative statin.
- Poor Function (CC): Two reduced-function alleles. Significantly reduced hepatic uptake. Highest myopathy risk. CPIC recommends avoiding simvastatin or using a low dose with careful monitoring.
Already have your DNA file? See your SLCO1B1 genotype and simvastatin safety context.
CPIC Clinical Guidelines
CPIC has published a Level A guideline (strongest evidence) for the SLCO1B1–simvastatin interaction. The guideline recommends adjusting simvastatin therapy based on SLCO1B1 genotype to reduce myopathy risk:
- Normal Function (TT): Standard simvastatin prescribing. No genotype-based adjustments needed.
- Intermediate Function (TC): Prescribe a lower simvastatin dose or consider an alternative statin (e.g., pravastatin, rosuvastatin) that is less dependent on OATP1B1 transport.
- Poor Function (CC): Avoid simvastatin or use a low dose only with careful monitoring. An alternative statin with lower myopathy risk is generally preferred.
The guideline also notes that the 80 mg simvastatin dose carries the highest myopathy risk and was restricted by the FDA in 2011 for new patients, independent of genotype.
Get Your SLCO1B1 Results
The key SLCO1B1 variant rs4149056 is well-covered on consumer genotyping arrays from 23andMe, AncestryDNA, and other services. Upload your raw data to DecodeMyBio to learn your SLCO1B1 genotype. Your Medication Safety Report will include your SLCO1B1 genotype, function category, and the simvastatin interaction context. See our methodology for details and our limitations page for what consumer-grade analysis cannot cover.
For a walkthrough of what you can do with consumer DNA data, see what to do with your 23andMe raw data and our guide to raw DNA pharmacogenomic analysis.
Get your Medication Safety Report. Upload your raw DNA data to see your SLCO1B1 results and statin safety profile.
Frequently Asked Questions
What does SLCO1B1 do?
SLCO1B1 encodes the OATP1B1 transporter protein, which moves certain drugs — including statins — from the bloodstream into liver cells. It is not a drug-metabolizing enzyme; it is a drug transporter.
How does SLCO1B1 affect statin side effects?
Reduced SLCO1B1 function leads to higher statin concentrations in the bloodstream and increased muscle tissue exposure, raising the risk of myopathy — muscle pain, weakness, and in rare cases, rhabdomyolysis.
What is the rs4149056 variant?
rs4149056 (c.521T>C) is the most clinically significant SLCO1B1 variant. The C allele reduces OATP1B1 transporter function. One C allele (TC) gives intermediate function; two C alleles (CC) gives poor function.
Is SLCO1B1 a drug-metabolizing enzyme?
No. SLCO1B1 encodes a transporter, not an enzyme. It controls how effectively drugs reach the liver, not how fast they are broken down once there.
How common is reduced SLCO1B1 function?
The rs4149056 C allele frequency is approximately 15–20% in European populations and 2–5% in East Asian and African populations. About 1–3% of Europeans carry the CC (poor function) genotype.
Can consumer DNA tests detect SLCO1B1 variants?
Yes. The key variant rs4149056 is well-covered on consumer genotyping arrays from 23andMe, AncestryDNA, and other services, enabling reliable SLCO1B1 genotype determination.
Beyond Medications: Nutrition and Methylation
If you're exploring how your DNA affects nutrition or methylation, your raw data also contains variants in genes like MTHFR, FUT2, VDR, and others that influence nutrient metabolism. See our Nutrition & Methylation Report for a nutrigenomic analysis from the same DNA data.
Last reviewed: February 2026 · DecodeMyBio Editorial Team