SLCO1B1 (Solute Carrier Organic Anion Transporter Family Member 1B1): SLCO1B1 is a transporter protein that helps move drugs, including statins, into liver cells for metabolism. Genetic variations in SLCO1B1 can reduce transporter function, leading to higher drug levels in the blood and an increased risk of statin-induced muscle side effects. Testing SLCO1B1 can help guide statin selection and dosing to minimize adverse effects.