USMLE Cheat Sheet 2026

The 30 highest-yield USMLE facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Which enzyme catalyzes the rate-limiting step of fatty acid synthesis? → Acetyl-CoA carboxylase
2. Choose the correct answer → Cricothyroid
3. Which bacterial toxin is responsible for the classic symptoms of tetanus by blocking inhibitory neurotransmitter release? → Tetanospasmin (blocks GABA/glycine release at inhibitory interneurons)
4. A patient presents with periorbital and peripheral edema, massive proteinuria (>3.5 g/day), hypoalbuminemia, and hyperlipidemia. What is this syndrome? → Nephrotic syndrome
5. Choose the correct answer → Bacillus cereus
6. Which phase of the cardiac action potential in ventricular cardiomyocytes is responsible for the prolonged plateau and is mediated by L-type calcium channels? → Phase 2 (plateau phase)
7. Which vitamin is a cofactor for pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and transketolase? → Thiamine (B1)
8. A child presents with megaloblastic anemia and homocystinuria but normal methylmalonic acid levels. Which vitamin deficiency is most likely? → Folate
9. A patient on methotrexate develops mucositis and bone marrow suppression. Which agent is given to rescue normal cells? → Leucovorin (folinic acid)
10. Choose the correct answer → Staphylococcus epidermidis
11. Choose the correct answer → “I left your mother, I didn’t leave you.”
12. A patient with type 2 diabetes develops lactic acidosis. Which medication is most likely responsible? → Metformin
13. Which beta-blocker is cardioselective and preferred in a patient with COPD requiring beta-blockade? → Metoprolol
14. Choose the correct answer → 5α-reductase deficiency
15. A young woman presents with a butterfly rash, arthritis, and proteinuria. ANA is positive. Which antibody is most specific for SLE? → Anti-Smith
16. A 30-year-old woman has a breast mass that moves freely, is rubbery, and has well-defined borders. No lymph node involvement. What is the most likely diagnosis? → Fibroadenoma
17. Choose the correct answer → Panacinar
18. A patient with chronic myeloid leukemia (CML) has the Philadelphia chromosome. Which genetic translocation produces this? → t(9;22)
19. Which tumor marker is elevated in hepatocellular carcinoma? → Alpha-fetoprotein (AFP)
20. Lesch-Nyhan syndrome is caused by deficiency of which enzyme? → HGPRT (hypoxanthine-guanine phosphoribosyltransferase)
21. Which drug is a selective serotonin reuptake inhibitor (SSRI) with the longest half-life and is used to minimize withdrawal syndrome? → Fluoxetine
22. A sputum culture grows gram-positive cocci in clusters that are catalase-positive and coagulase-positive. What organism is this? → Staphylococcus aureus
23. A CSF sample shows gram-negative diplococci. What is the most likely causative organism in an 18-year-old college student? → Neisseria meningitidis
24. The blood-testis barrier, which protects developing germ cells from immune surveillance, is formed by tight junctions between which cells? → Sertoli cells
25. Choose the correct answer → bcl-2 activation
26. Choose the correct answer → Vibratory sense from the ipsilateral arm
27. Which mechanism explains why aminoglycosides are bactericidal despite being protein synthesis inhibitors? → They cause misreading of mRNA, producing abnormal proteins that disrupt cell membranes
28. A patient develops torsades de pointes after starting a new antiarrhythmic. Which drug is most likely responsible? → Sotalol
29. Choose the correct answer → Diabetic ketoacidosis
30. Choose the correct answer → immotile sperm