Free Step 1 Cheat Sheet 2026: Exam Quick Reference

General Principles + Foundations

12-16%of exam

BiochemistryGeneticsMicrobiologyImmunologyCell + MolecularPharm Principles

Organ Systems + Pathology

60-75%of exam

CardiovascularRespiratory + RenalNeuro + BehavioralRepro + EndocrineGI + HemeMSK + Skin

Disciplines + Competencies

10-20%of exam

PathologyPhysiologyPharmacologyBiostatisticsCommunicationDiscipline 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

AFP=liver, CA-125=ovary, CEA=colon

AFP: hepatocellularCA-125: ovarianCEA: colorectalPSA: prostate

Exotoxin vs Endotoxin

Exotoxin

Secreted protein
Highly toxic
Toxoid vaccine

Endotoxin

LPS, gram-negative
Lysis released
No toxoid

Secreted vs membrane

Biochem + Genetics

Rate-limiting glycolysis: PFK-1
Tay-Sachs: Hexosaminidase ANo HSM
Gaucher: GlucocerebrosidaseHSM
PKU: Phenylalanine hydroxylase
Marfan: Fibrillin-1 (FBN1)
Anticipation: Trinucleotide repeats
Imprinting: Prader-Willi / Angelman
Mitochondrial: Maternal inheritance

Collagen Types

Type I bone, II cartilage, III vessels, IV membrane

I: bone/skinII: cartilageIII: reticulin/vesselsIV: basement membrane

Microbiology Bugs

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

Acetaminophen=NAC; opioid=naloxone; benzo=flumazenil

NAC: acetaminophenNaloxone: opioidsFlumazenil: benzodiazepinesFomepizole: alcohols

Immunology

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

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

MUDPILES

MethanolUremiaDKAPropylene glycolIron/INHLactateEthylene glycolSalicylates

Transudate vs Exudate

Transudate

Low protein
Pressure-driven
CHF, cirrhosis

Exudate

High protein
Inflammation-driven
Infection, malignancy

Pressure vs inflammation

Anemia Workup

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

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%

Necrosis vs Apoptosis

Necrosis

Cell swelling
Membrane rupture
Inflammation

Apoptosis

Cell shrinkage
Membrane intact
No inflammation

Pathologic vs programmed

Acid-Base Picker

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

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

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

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

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

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

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

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

Sensitivity vs Specificity

Sensitivity

True positive rate
Screening test
SnNout rules out

Specificity

True negative rate
Confirmatory test
SpPin rules in

Screen vs confirm

Study Design Picker

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

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: +$205 outside US/Canada

Cohort vs Case-Control

Cohort

Exposure first
Relative risk
Prospective common

Case-Control

Outcome first
Odds ratio
Retrospective, rare disease

Forward vs backward

Biostatistics

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

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 3-4 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

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