USMLE Step 1 High Yield Topics: A System-by-System List (2026)
Written by Dr Zartasha Ali, MBBS, FCPS (Medicine). Reviewed by Dr Ammar Hussain, MBBS, FCPS (Pediatrics), MRCPCH.
The high-yield topics for USMLE Step 1 are the core mechanisms of disease in each organ system, with pathology and physiology carrying the most weight. The official specifications give pathology 45 to 55 per cent of the exam and physiology 30 to 40 per cent. The lists below name the topics we would revise first in each system.
The topic lists are our authors’ teaching judgement about commonly emphasised medical topics, organised by the official USMLE content outline. The percentages are the USMLE’s own, read on usmle.org on 14 October 2026.
What “high yield” means on Step 1
A topic is high yield when it meets three tests.
- It sits in a heavily weighted area. The official tables show where the questions are.
- It explains other topics. The Frank-Starling curve explains heart failure, shock and the action of several drugs.
- It can be asked as a mechanism. The specifications say 60 to 70 per cent of Step 1 is “Medical Knowledge: Applying Foundational Science Concepts”.
A rare disease with one memorable fact is low yield by these tests. A common disease with a clear mechanism is high yield.
Most important subjects for USMLE Step 1
The official discipline table ranks the subjects. The ranges add up to more than 100 per cent because one question can count toward several disciplines.
| Discipline | Range, % |
|---|---|
| Pathology | 45-55 |
| Physiology | 30-40 |
| Nutrition | 15-20 |
| Gross Anatomy & Embryology | 10-20 |
| Microbiology | 10-20 |
| Pharmacology | 10-20 |
| Behavioral Sciences | 10-15 |
| Biochemistry | 5-15 |
| Histology & Cell Biology | 5-15 |
| Immunology | 5-15 |
| Genetics | 5-10 |
Source: USMLE Step 1 Content Outline and Specifications, Table 3.
The system table tells you where those disciplines are tested.
| System | Range, % |
|---|---|
| Reproductive & Endocrine Systems | 12-16 |
| Respiratory & Renal/Urinary Systems | 11-15 |
| Behavioral Health & Nervous Systems/Special Senses | 10-14 |
| Blood & Lymphoreticular/Immune Systems | 9-13 |
| Musculoskeletal, Skin & Subcutaneous Tissue | 8-12 |
| Multisystem Processes & Disorders | 8-12 |
| Cardiovascular System | 7-11 |
| Gastrointestinal System | 6-10 |
| Social Sciences: Communication and Interpersonal Skills | 6-9 |
| Biostatistics & Epidemiology/Population Health | 4-6 |
| Human Development | 1-3 |
Source: USMLE Step 1 Content Outline and Specifications, Table 1, sorted here from largest to smallest.
The full tables, with the official footnotes, are in our guide to what is on USMLE Step 1.
Highest yield topics for Step 1, system by system
Reproductive and endocrine systems (12-16%)
- Hypothalamic-pituitary axes and feedback loops
- Diabetes mellitus: type 1 and type 2, diabetic ketoacidosis, insulin and oral drugs
- Thyroid disease: Graves disease, Hashimoto thyroiditis, thyroid cancers
- Adrenal disorders: Cushing syndrome, Addison disease, congenital adrenal hyperplasia, pheochromocytoma
- Calcium and parathyroid hormone; multiple endocrine neoplasia syndromes
- The menstrual cycle, hormonal contraception, polycystic ovary syndrome
- Pregnancy physiology, pre-eclampsia, ectopic pregnancy, hydatidiform mole
- Breast, ovarian, cervical, testicular and prostate tumours
- Sexual differentiation and its disorders, including Turner and Klinefelter syndromes
Respiratory and renal/urinary systems (11-15%)
- Lung volumes, compliance and the flow-volume loop
- Ventilation-perfusion matching and the causes of hypoxaemia
- Obstructive disease (asthma, COPD) against restrictive disease
- Pneumonia by organism, tuberculosis, lung cancer types
- Pulmonary embolism and pulmonary hypertension
- Acid-base disorders and the anion gap
- Nephron transport and where each diuretic acts
- Nephritic and nephrotic syndromes
- Acute kidney injury: prerenal, intrinsic and postrenal causes
- Sodium, potassium and water balance; renal tubular acidosis; kidney stones
Behavioral health and nervous systems, special senses (10-14%)
- Spinal cord tracts and the classic cord lesions
- Brainstem and cranial nerve lesions; stroke syndromes by artery
- Neurotransmitters and the drugs that act on them
- Seizures and antiepileptic drugs; Parkinson disease; dementia types
- Demyelinating disease, meningitis, brain tumours
- Mood, anxiety and psychotic disorders with their drug classes and adverse effects
- Substance intoxication and withdrawal
- Sleep stages; defence mechanisms
- Visual field defects, the pupillary reflex, hearing loss tests
Blood and lymphoreticular/immune systems (9-13%)
- Anaemias: microcytic, macrocytic, haemolytic
- Haemoglobin disorders: sickle cell disease, thalassaemias
- The coagulation cascade, bleeding disorders, anticoagulant drugs
- Leukaemias and lymphomas with their key translocations
- The four types of hypersensitivity
- Immunodeficiency syndromes
- Transplant rejection and immunosuppressant drugs
- Complement, immunoglobulin classes, vaccines
- Blood transfusion reactions
Musculoskeletal, skin and subcutaneous tissue (8-12%)
- Brachial plexus and lumbosacral plexus injuries
- Rotator cuff, knee ligaments, common fractures and the nerves at risk
- Osteoarthritis against rheumatoid arthritis; gout and pseudogout
- Systemic lupus erythematosus, scleroderma, vasculitis syndromes
- Bone tumours, osteoporosis, Paget disease of bone
- Muscular dystrophies and the neuromuscular junction (myasthenia gravis, Lambert-Eaton syndrome)
- Skin cancers, blistering diseases, common rashes and skin infections
Multisystem processes and disorders (8-12%)
- Cell injury, necrosis types, apoptosis
- Acute and chronic inflammation, wound healing
- Neoplasia: oncogenes, tumour suppressors, tumour markers, paraneoplastic syndromes
- Vitamins and minerals: deficiency and toxicity
- Inheritance patterns, trisomies, trinucleotide repeat disorders
- Lysosomal and glycogen storage diseases
- Shock, sepsis and systemic infections such as HIV
- Autonomic pharmacology, pharmacokinetics, drug toxicities and antidotes
Cardiovascular system (7-11%)
- The cardiac cycle, pressure-volume loops, heart sounds and murmurs
- Cardiac output, preload and afterload
- Action potentials and the classes of antiarrhythmic drugs
- Atherosclerosis, angina and myocardial infarction, with ECG territory and complications by time
- Heart failure and the drugs that improve survival
- Hypertension and antihypertensive drugs
- Congenital heart disease and fetal circulation
- Endocarditis, rheumatic fever, cardiomyopathies, pericardial disease
Gastrointestinal system (6-10%)
- Gut hormones and the control of acid secretion
- Peptic ulcer disease and Helicobacter pylori
- Crohn disease against ulcerative colitis; coeliac disease
- Viral hepatitis serology, especially hepatitis B
- Cirrhosis, portal hypertension and bilirubin metabolism
- Gallstones and pancreatitis
- Colorectal cancer and the polyposis syndromes
- Infectious diarrhoea by organism
- Blood supply of the gut and embryological defects of the gut tube
Social sciences: communication and interpersonal skills (6-9%)
- Informed consent, capacity and minors
- Confidentiality and its exceptions
- Delivering bad news; responding to an angry or grieving patient
- Advance directives and surrogate decision-makers
- Disclosing medical errors
- Working with interpreters and respecting cultural beliefs
Biostatistics and epidemiology/population health (4-6%)
- Sensitivity, specificity and predictive values
- Relative risk, odds ratio, number needed to treat
- Study designs and their typical biases
- Type I and type II error, power, confidence intervals, p values
- Choosing a statistical test
- Incidence against prevalence; levels of prevention
- Quality improvement and patient safety concepts
Human development (1-3%)
- Developmental milestones in infants and children
- Normal changes of ageing
- Screening and vaccination of the well patient
How to use this list
Use the list as a gap check, not as a course.
- Mark each topic. Give it one of three marks: can explain it aloud, can recognise it, cannot recall it.
- Fix the third group first. Read the topic in your main textbook or review book, then do questions on it the same day.
- Test the second group with questions. Recognition feels like knowledge but fails under exam conditions.
- Return in a week. A topic counts as learned when you can recall it after a gap.
This is active recall with spacing. Our USMLE Step 1 study schedule explains the method and builds it into a weekly plan.
Five mechanisms that cross every system
Some concepts appear inside many systems. Time spent on them is repaid several times.
| Concept | Where it returns |
|---|---|
| Autonomic receptors | Cardiovascular drugs, asthma, bladder, eye, shock |
| Inflammation and repair | Every pathology chapter |
| Acid-base balance | Renal, respiratory, endocrine (diabetic ketoacidosis), gastrointestinal losses |
| Hypersensitivity types | Immunology, renal, skin, drug reactions, transfusion |
| Pressure, flow and resistance | Cardiovascular, respiratory, renal blood flow |
USMLE Step 1 high yield notes PDF: should you use one?
Short “high-yield notes” files are popular because they look manageable. They have two limits.
First, a list of facts does not train the main task of the exam. Most Step 1 questions ask you to apply a concept to a patient.
Notes help you revise a mechanism you already understand. They do not teach it.
Second, many shared PDF files have no named author and no date. You cannot tell whether a fact is current or correct.
A safer approach is to make your own one-page summary for each system from your main resources. Writing it is itself a form of active recall. Keep it for the last two weeks before the exam.
Our papers are read online while logged in, and are not supplied as PDF downloads.
What a topic list cannot tell you
No topic list can tell you which questions will be on your exam. The USMLE publishes percentage ranges for systems and disciplines, not topic frequencies. The official page also warns that “percentages are subject to change at any time.”
The lists on this page reflect what medical teachers generally treat as core content. A topic missing from the list can still be tested. Use the official content outline as the full boundary of the exam, and use this page to decide the order of your revision.
Practising the high-yield topics
After you revise a system, test it with questions written for that system. Our authors write recall questions for each system and discipline in the official outline. You can see them on the USMLE Step 1 recalls page, each with free sample questions.
Questions people ask
What are the highest yield topics for Step 1?
By official weight, pathology and physiology are the highest-yield disciplines. Reproductive and endocrine systems, and respiratory and renal systems, are the largest system categories. Within them, the mechanisms of common diseases come first.
Which subject should I study first for Step 1?
Start with physiology and general pathology. Both are needed to understand the organ systems. Biochemistry, immunology and microbiology fit well before or alongside the first systems.
Is biochemistry high yield for Step 1?
Biochemistry is listed at 5 to 15 per cent, and nutrition separately at 15 to 20 per cent. Vitamins, metabolic pathways with clinical disorders, and storage diseases are the parts we would revise first.
Is biostatistics worth the time?
Yes. Biostatistics and epidemiology make up 4 to 6 per cent of the exam. The topic list is short and the calculations follow fixed rules.
How many high-yield topics are there?
There is no official number. The USMLE does not publish a high-yield list. Any list, including this one, is a teaching aid.
Are ethics and communication questions high yield?
They are 6 to 9 per cent of the exam under the official heading “Social Sciences: Communication and Interpersonal Skills”. The principles are few, so the return on study time is high.
Sources
All pages were opened on 14 October 2026.
- USMLE Step 1 Content Outline and Specifications: https://www.usmle.org/exam-resources/step-1-materials/step-1-content-outline-and-specifications
- USMLE Step 1 Exam Content: https://www.usmle.org/step-exams/step-1/step-1-exam-content
- USMLE Step 1 Formats and Questions: https://www.usmle.org/exam-resources/step-1-materials/step-1-test-question-formats