USMLE Step 1 Cheat Sheet

Foundational Science

Not published of exam
Biochemistry Genetics Microbiology Immunology Cell + Molecular Pharm Principles

Organ Systems + Pathology

60-75% of exam
Cardiovascular Respiratory + Renal Neuro + Behavioral Repro + Endocrine GI + Heme MSK + Skin

Disciplines + Competencies

10-20% of exam
Pathology Physiology Pharmacology Biostatistics Communication Discipline Picker

Quick Facts

Exam USMLE Step 1
Scoring Pass/Fail only
Pass/Fail since Jan 26 2022
Questions Up to 280
Blocks 14 x 30 min
Per block Up to 20
Session 8-hour day
Fee $695 (2026)

Tumor Markers FO

AFP=liver, CA-125=ovary, CEA=colon
AFP: hepatocellular CA-125: ovarian CEA: colorectal PSA: prostate

Exotoxin vs Endotoxin FO

Exotoxin

Secreted protein
Highly toxic
Toxoid vaccine

Endotoxin

LPS, gram-negative
Lysis released
No toxoid
Secreted vs membrane

Biochem + Genetics FO

Rate-limiting glycolysis PFK-1
Tay-Sachs Hexosaminidase A No HSM
Gaucher Glucocerebrosidase HSM
PKU Phenylalanine hydroxylase
Marfan Fibrillin-1 (FBN1)
Anticipation Trinucleotide repeats
Imprinting Prader-Willi / Angelman
Mitochondrial Maternal inheritance

Collagen Types FO

Type I bone, II cartilage, III vessels, IV membrane
I: bone/skin II: cartilage III: reticulin/vessels IV: basement membrane

Microbiology Bugs FO

Currant-jelly sputum Klebsiella
Rusty sputum S. pneumoniae
Rice-water stools Vibrio cholerae
Bull's-eye rash Borrelia (Lyme)
Sulfur granules Actinomyces
Owl-eye inclusions CMV
Negri bodies Rabies
Tumbling motility Listeria

Antidote Recall FO

Acetaminophen=NAC; opioid=naloxone; benzo=flumazenil
NAC: acetaminophen Naloxone: opioids Flumazenil: benzodiazepines Fomepizole: alcohols

Immunology FO

Type I IgE, mast cells
Type II Antibody, cell-bound
Type III Immune complexes
Type IV T-cell delayed
MHC I CD8, all cells
MHC II CD4, APCs
Th1 IFN-gamma, macrophages
Th2 IL-4/5, B cells

Pharm + Antidotes FO

Acetaminophen N-acetylcysteine
Opioids Naloxone
Benzodiazepines Flumazenil
Warfarin Vitamin K, FFP
Heparin Protamine sulfate
Organophosphates Atropine + pralidoxime
Methanol/ethylene glycol Fomepizole
Digoxin Digoxin Fab antibodies

High Anion Gap SY

MUDPILES
Methanol Uremia DKA Propylene glycol Iron/INH Lactate Ethylene glycol Salicylates

Transudate vs Exudate SY

Transudate

Low protein
Pressure-driven
CHF, cirrhosis

Exudate

High protein
Inflammation-driven
Infection, malignancy
Pressure vs inflammation

Anemia Workup SY

Low MCV → Microcytic ( Iron, thalassemia )
Normal MCV → Normocytic
High MCV → Macrocytic ( B12, folate )
High reticulocytes → Hemolytic / blood loss
Low reticulocytes → Marrow failure
Hypersegmented neutrophils → B12 or folate
Neuro deficits → B12 deficiency ( Not folate )
Schistocytes present → Microangiopathic hemolysis

System Weights SY

Repro + endocrine 12-16%
Respiratory + renal 11-15%
Behavioral + nervous 10-14%
Blood + lymph/immune 9-13%
MSK + skin 8-12%
Multisystem 8-12%
Cardiovascular 7-11%
Gastrointestinal 6-10%
Communication/social 6-9%
Biostats/epidemiology 4-6%
Human development 1-3%

Necrosis vs Apoptosis SY

Necrosis

Cell swelling
Membrane rupture
Inflammation

Apoptosis

Cell shrinkage
Membrane intact
No inflammation
Pathologic vs programmed

Acid-Base Picker SY

Low pH, low HCO3 → Metabolic acidosis
High anion gap → MUDPILES causes
Normal anion gap → Diarrhea / RTA
Low pH, high CO2 → Respiratory acidosis
High pH, high HCO3 → Metabolic alkalosis
High pH, low CO2 → Respiratory alkalosis
Winter formula off → Mixed disorder

Cardio + Pulm + Renal SY

Pulsus paradoxus Cardiac tamponade
Boot-shaped heart Tetralogy of Fallot
S3 gallop Heart failure
Curschmann spirals Asthma
Honeycomb lung Pulmonary fibrosis
Kimmelstiel-Wilson Diabetic nephropathy
RBC casts Glomerulonephritis
Muddy-brown casts Acute tubular necrosis

Neuro + Endocrine SY

Lewy bodies Parkinson disease
Neurofibrillary tangles Alzheimer disease
Negri-like, hyperphagia Kluver-Bucy
Whorled psammoma bodies Meningioma
Hurthle cells Hashimoto thyroiditis
Orphan Annie nuclei Papillary thyroid cancer
Pheochromocytoma Episodic hypertension
Waterhouse-Friderichsen Adrenal hemorrhage

GI + Heme + MSK SY

Anti-mitochondrial antibody Primary biliary cholangitis
String sign Crohn disease
Mallory bodies Alcoholic hepatitis
Auer rods Acute myeloid leukemia
Smudge cells CLL
Reed-Sternberg cells Hodgkin lymphoma
Bamboo spine Ankylosing spondylitis
Anti-CCP Rheumatoid arthritis

2x2 Table CO

Sens/Spec down columns; PPV/NPV across rows
Sens: TP/(TP+FN) Spec: TN/(TN+FP) PPV: TP/(TP+FP) NPV: TN/(TN+FN)

Pass vs Fail Report CO

Pass

No numeric score
No content feedback
Single outcome

Fail

Content areas given
Distance from passing
Guides retake
Pass quiet vs fail detailed

Discipline Picker CO

Disease mechanism asked → Pathology ( Highest yield )
Normal function asked → Physiology
Drug + side effect → Pharmacology
Enzyme deficiency → Biochemistry
Organism identification → Microbiology
Antibody / hypersensitivity → Immunology
Study design / stats → Biostatistics
Patient counseling → Communication skills

Discipline Weights CO

Pathology 45-55% Highest yield
Physiology 30-40%
Nutrition 15-20%
Gross anatomy + embryo 10-20%
Microbiology 10-20%
Pharmacology 10-20%
Behavioral sciences 10-15%
Biochemistry 5-15%
Histology + cell biol 5-15%
Immunology 5-15%

Sensitivity vs Specificity CO

Sensitivity

True positive rate
Screening test
SnNout rules out

Specificity

True negative rate
Confirmatory test
SpPin rules in
Screen vs confirm

Study Design Picker CO

Exposure then outcome → Cohort study
Outcome then exposure → Case-control study
Snapshot prevalence → Cross-sectional study
Random assignment → Randomized trial
Pool many studies → Meta-analysis

Exam Logistics CO

Items Up to 280
Blocks 14 blocks
Block time 30 minutes
Per block Up to 20
Break time 55 min minimum
Tutorial 5-min optional
Fee 2026 $695
Region fee +$210 outside US/Canada

Cohort vs Case-Control CO

Cohort

Exposure first
Relative risk
Prospective common

Case-Control

Outcome first
Odds ratio
Retrospective, rare disease
Forward vs backward

Biostatistics CO

Sensitivity Rules out (SnNout)
Specificity Rules in (SpPin)
PPV Rises with prevalence
NPV Falls with prevalence
Relative risk Cohort studies
Odds ratio Case-control studies
Type I error False positive (alpha)
Type II error False negative (beta)

Scoring Rules CO

Outcome Pass or fail
Numeric score Not reported
Equivalent standard 196 prior scale
Pass feedback No content feedback
Fail feedback Content areas given
Attempt cap 4 per Step
Annual limit 3 per 12 months
Result timing Usually 2-4 weeks

Common Traps

Score vs outcome

No 3-digit score ≠ Pass/fail only

Sensitivity vs specificity

Sens screens out ≠ Spec confirms in

RR vs OR

RR for cohort ≠ OR for case-control

Exotoxin vs endotoxin

Exotoxin secreted protein ≠ Endotoxin gram-negative LPS

B12 vs folate

B12 has neuro ≠ Folate no neuro

Necrosis vs apoptosis

Necrosis inflames ≠ Apoptosis silent

Step 1 vs MCAT

Step 1 licenses physicians ≠ MCAT is admissions

Last Minute

1. Pass/Fail only since 2022
2. No numeric score reported
3. 14 blocks, 30 min each
4. Up to 280 items total
5. Pathology highest discipline weight
6. Sens screens; Spec confirms
7. RR cohort; OR case-control
8. B12 deficiency has neuro signs
9. Exotoxin protein; endotoxin LPS
10. Acetaminophen antidote is NAC

USMLE Step 1

Practice Questions 200 questions Study Guide 24 topics Cheat Sheet 101 facts Flashcards 50 cards Games 20 terms Shorts 1 short Videos 1 video Blogs 1 blog 1 Job Wiki Free CE Podcast
Word games 20 terms Guess the Term T E R M S Read the clue and guess the term in 6 tries. Word games 20 terms Term Match Swap tiles to line up three of the same term. Word games 20 terms Term Pairs ? ✓ ✓ ? ? Flip two cards at a time to find matching terms. Word games 20 terms Term Search Q T E R M X Find five hidden terms in a grid of letters.