200+ Free USMLE Step 1 Practice Questions

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Question 1

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A 45-year-old man presents with fatigue and jaundice. Laboratory studies show elevated unconjugated bilirubin. Which enzyme deficiency is most likely responsible for this presentation?

Glucose-6-phosphate dehydrogenase

UDP-glucuronosyltransferase

Phenylalanine hydroxylase

Homogentisic acid oxidase

to track

2026 Statistics

Key Facts: USMLE Step 1 Exam

91%

US/Canadian MD Pass Rate

USMLE 2023

280

Maximum Questions

USMLE Content Outline

Total Testing Time

USMLE

Question Blocks

USMLE

44-52%

Pathology Content

USMLE Content Description

$670

Exam Fee

2026 USMLE Fee Schedule

USMLE Step 1 transitioned to Pass/Fail scoring in January 2022. The exam consists of up to 280 questions across 7 blocks with 8 hours total testing time. First-time pass rates for US/Canadian MD students are approximately 91%, while DO students average 96% and international graduates 82%. The exam emphasizes integrated systems-based thinking and clinical vignettes requiring application of basic science knowledge to patient care scenarios.

Sample USMLE Step 1 Practice Questions

Try these sample questions to test your USMLE Step 1 exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 200+ question experience with AI tutoring.

1A 45-year-old man presents with fatigue and jaundice. Laboratory studies show elevated unconjugated bilirubin. Which enzyme deficiency is most likely responsible for this presentation?

A.Glucose-6-phosphate dehydrogenase

B.UDP-glucuronosyltransferase

C.Phenylalanine hydroxylase

D.Homogentisic acid oxidase

Explanation: UDP-glucuronosyltransferase is responsible for conjugating bilirubin in the liver. Deficiency (as in Gilbert syndrome or Crigler-Najjar syndrome) results in unconjugated hyperbilirubinemia. G6PD deficiency causes hemolytic anemia with indirect hyperbilirubinemia but is not an enzyme deficiency in the liver conjugation pathway.

2A 2-year-old child presents with developmental delay, intellectual disability, and a musty odor to the urine. Which dietary restriction is essential for this patient?

A.Galactose

B.Phenylalanine

C.Fructose

D.Leucine

Explanation: Phenylketonuria (PKU) is caused by phenylalanine hydroxylase deficiency, leading to accumulation of phenylalanine and its metabolites. The musty odor is from phenylacetic acid. Treatment requires lifelong restriction of phenylalanine intake.

3A researcher is studying a signaling pathway where a ligand binds to a receptor tyrosine kinase, leading to cell proliferation. Which of the following is the most likely downstream signaling molecule in this pathway?

A.cAMP

B.Ras protein

C.IP3

D.Nitric oxide

Explanation: Receptor tyrosine kinases (RTKs) typically signal through the Ras-MAPK pathway for cell proliferation. cAMP is associated with G-protein coupled receptors (Gs), IP3 with Gq-coupled receptors, and nitric oxide with soluble guanylate cyclase signaling.

4A 6-month-old infant presents with fasting hypoglycemia, hepatomegaly, and lactic acidosis. A liver biopsy shows glycogen accumulation. Which enzyme deficiency is most likely?

A.Glucose-6-phosphatase

B.Glycogen phosphorylase

C.Branching enzyme

D.Debranching enzyme

Explanation: Glucose-6-phosphatase deficiency (von Gierke disease or Type I glycogen storage disease) presents with severe fasting hypoglycemia, lactic acidosis, hyperuricemia, and hepatomegaly due to glycogen and fat accumulation in the liver.

5A patient with a history of alcohol abuse presents with neurological symptoms including ophthalmoplegia, ataxia, and confusion. Which vitamin deficiency is most likely responsible?

A.Vitamin B12

B.Thiamine (Vitamin B1)

C.Folate

D.Niacin

Explanation: The triad of ophthalmoplegia (CN III, IV, VI palsies), ataxia, and confusion is classic for Wernicke encephalopathy caused by thiamine deficiency, commonly seen in alcoholics. Untreated, this can progress to Korsakoff psychosis.

6A newborn presents with lethargy, vomiting, and jaundice shortly after introducing breast milk. Laboratory studies show elevated galactose and galactitol in the blood. Which enzyme is deficient?

A.Galactokinase

B.Galactose-1-phosphate uridyltransferase

C.Lactase

D.Aldolase B

Explanation: Classic galactosemia is caused by galactose-1-phosphate uridyltransferase deficiency. Symptoms appear with lactose/galactose ingestion and include vomiting, jaundice, hepatomegaly, cataracts, and intellectual disability if untreated.

7A patient with chronic granulomatous disease develops recurrent infections with catalase-positive organisms. What is the underlying defect in this condition?

A.Defective neutrophil chemotaxis

B.Defective NADPH oxidase complex

C.Defective CD18 integrin

D.Defective myeloperoxidase

Explanation: Chronic granulomatous disease (CGD) is caused by defects in the NADPH oxidase complex, preventing the respiratory burst and superoxide generation needed to kill catalase-positive organisms like Staphylococcus aureus, Burkholderia cepacia, and Aspergillus.

8A cell line is found to have a mutation in the p53 gene. Which cellular process is most likely impaired?

A.DNA repair and cell cycle checkpoint control

B.Protein synthesis initiation

C.Lipid metabolism

D.Glycolysis regulation

Explanation: p53 is the "guardian of the genome" that regulates cell cycle checkpoints (G1/S arrest), DNA repair, and apoptosis in response to DNA damage. Loss of p53 function is the most common genetic alteration in human cancers.

9A patient presents with muscle weakness and myoglobinuria after vigorous exercise. Which metabolic pathway is most likely impaired?

A.Gluconeogenesis

B.Glycogenolysis

C.Fatty acid oxidation

D.Ketogenesis

Explanation: McArdle disease (Type V glycogen storage disease) and fatty acid oxidation defects can cause exercise intolerance with myoglobinuria. However, McArdle disease causes a second wind phenomenon. Fatty acid oxidation defects present with non-ketotic hypoglycemia and cardiomyopathy.

10Which enzyme catalyzes the rate-limiting step in cholesterol synthesis?

A.HMG-CoA synthase

B.HMG-CoA reductase

C.HMG-CoA lyase

D.Acetyl-CoA carboxylase

Explanation: HMG-CoA reductase catalyzes the conversion of HMG-CoA to mevalonate, the rate-limiting step in cholesterol synthesis. It is the target of statin drugs. HMG-CoA lyase is involved in ketogenesis, and acetyl-CoA carboxylase is the rate-limiting enzyme in fatty acid synthesis.

About the USMLE Step 1 Exam

USMLE Step 1 assesses foundational understanding of health, disease, and therapeutic principles across organ systems. The exam covers general principles (12-16%), behavioral health & nervous system (9-13%), reproductive & endocrine (9-13%), respiratory & renal (9-13%), blood & lymph (7-11%), multisystem processes (6-10%), musculoskeletal & skin (6-10%), cardiovascular (5-9%), gastrointestinal (5-9%), and biostatistics (4-6%). Content is organized by disciplines: pathology (44-52%), physiology (25-35%), pharmacology (15-22%), and biochemistry/nutrition (14-24%).

Questions

280 scored questions

Time Limit

8 hours (7 × 60-minute blocks)

Passing Score

Pass/Fail (since January 2022)

Exam Fee

$670 (FSMB and NBME)

USMLE Step 1 Exam Content Outline

12-16%

General Principles

Biochemistry, molecular biology, cell biology, genetics, immunology, microbiology - foundational sciences applied clinically

9-13%

Behavioral Health & Nervous System

Psychology, psychiatry, neuroscience, and neurological disorders with emphasis on clinical presentation and mechanism

9-13%

Reproductive & Endocrine

Male and female reproductive systems, pregnancy, endocrine physiology and pathology, hormone regulation

9-13%

Respiratory & Renal

Pulmonary physiology and pathology, acid-base balance, renal function, electrolyte disorders

7-11%

Blood & Lymph

Hematopoiesis, coagulation, anemia, leukemias, lymphomas, immune-mediated blood disorders

6-10%

Multisystem Processes

Shock, sepsis, multisystem organ failure, autoimmune diseases, infectious diseases affecting multiple systems

6-10%

Musculoskeletal & Skin

Bone and joint disorders, connective tissue diseases, dermatology, wound healing, trauma

5-9%

Cardiovascular

Cardiac physiology, electrophysiology, congenital and acquired heart disease, vascular pathology

5-9%

Gastrointestinal

Digestive physiology, liver and pancreatic function, GI pathology, nutrition, metabolic disorders

4-6%

Biostatistics & Epidemiology

Study design, statistical interpretation, public health, screening test characteristics, evidence-based medicine

How to Pass the USMLE Step 1 Exam

What You Need to Know

Passing score: Pass/Fail (since January 2022)
Exam length: 280 questions
Time limit: 8 hours (7 × 60-minute blocks)
Exam fee: $670

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

USMLE Step 1 Study Tips from Top Performers

1Master pathology mechanisms - understand the 'why' behind disease processes, not just facts

2Practice clinical vignettes extensively - Step 1 emphasizes application of basic science to patient scenarios

3Use spaced repetition for memorization-heavy topics like microbiology, pharmacology, and biochemistry

4Focus on high-yield systems: general principles, cardiovascular, respiratory, renal, and GI

5Review biostatistics thoroughly - these concepts are often under-studied but consistently tested

Frequently Asked Questions

What is the USMLE Step 1 pass rate?

First-time pass rates vary by candidate type: US/Canadian MD students ~91%, DO students ~96%, US/Canadian IMGs ~82%, and non-US IMGs ~73% (2023 data). Pass/Fail scoring began January 26, 2022.

How is USMLE Step 1 scored?

Since January 2022, Step 1 is Pass/Fail only. Previously, it was scored on a three-digit scale (passing was 194, then 196). The change was made to reduce overemphasis on scores for residency applications.

How many questions are on USMLE Step 1?

The exam contains up to 280 multiple-choice questions divided into 7 blocks of up to 40 questions each. Each block is timed at 60 minutes. Total testing time is 8 hours including break time.

How long should I study for Step 1?

Most students dedicate 4-8 weeks of dedicated study time, with 6-8 hours of focused study daily. Total preparation typically spans 6-12 months of ongoing review during preclinical years plus dedicated study period.

What is the best way to prepare for Step 1?

Use a combination of resources: question banks (UWorld, NBME practice exams), first-aid review book, and pathology resources. Focus on understanding mechanisms and clinical applications rather than rote memorization.

Can I retake Step 1 if I fail?

Yes, you can retake Step 1 up to 4 times total, with a maximum of 3 attempts within a 12-month period. You must wait 28 days between attempts.