CLS Study Guide 2026
Everything you need to pass the CLS exam in one place: the exam format, every topic to study, real practice questions with explanations, flashcards, and full-length practice tests. Free, no sign-up needed.
📋 CLS Exam Format at a Glance
📚 CLS Topics to Study (21)
✍️ Sample CLS Questions & Answers
1. What is the Friedewald equation limitation regarding triglycerides when calculating LDL-C?
The Friedewald equation (LDL = TC − HDL − TG/5) becomes unreliable when triglycerides exceed 400 mg/dL because the VLDL estimate is inaccurate.
2. What role does smoking cessation play in cardiovascular risk?
Smoking cessation significantly reduces cardiovascular risk by improving endothelial function, decreasing inflammation, and lowering blood pressure and heart rate. Within just a few years of quitting, the risk of heart attack and stroke drops substantially, eventually approaching that of a non-smoker. It is one of the most impactful lifestyle changes for cardiovascular health.
3. Which fibrate–statin combination carries the greatest risk of severe myopathy and rhabdomyolysis?
Gemfibrozil inhibits the glucuronidation pathway responsible for statin metabolism, raising statin plasma concentrations significantly and increasing the risk of myopathy and rhabdomyolysis; fenofibrate does not share this interaction.
4. Which omega-3 fatty acid formulation is FDA-approved at prescription doses specifically for severe hypertriglyceridemia (≥500 mg/dL)?
Both Vascepa (pure EPA) and Lovaza (EPA+DHA) are FDA-approved prescription omega-3 formulations for triglycerides ≥500 mg/dL.
5. What does HDL cholesterol help with?
HDL cholesterol plays a crucial role in reverse cholesterol transport, which is the process of cholesterol removal. It picks up excess cholesterol from cells and arterial walls and transports it back to the liver for processing and excretion. This helps prevent the buildup of plaque and protects against cardiovascular disease.
6. What is the primary function of lipids in the body?
Lipids are a diverse group of organic compounds essential for various biological functions. Their primary roles include long-term energy storage, as they are highly efficient at storing metabolic energy. Additionally, phospholipids are the fundamental building blocks of cell membranes, forming the lipid bilayer that defines cellular boundaries and regulates substance passage.