The Complete Step 2 CK Breakdown by Subject and How to Plan For Each Subject

This blog was originally posted on November 22, 2022, and updated by Dr. Ria Patel in November 2024.

The USMLE Step 2 CK is a challenging exam that tests a wide range of clinical knowledge and skills across multiple subjects. Understanding the Step 2 CK breakdown by subject is critical for creating an efficient study plan and prioritizing the most high-yield Step 2 topics.

This blog provides a detailed breakdown of the exam, including the percentage weight of each subject, high-yield topics to focus on, and practical strategies to streamline your preparation. Whether you’re deep into your study schedule or just getting started, this guide will help you navigate the key areas tested on Step 2 CK.

For official details, you can find the Step 2 CK content outline on the USMLE website.

Human Development (2-4%)

• This section focuses on age-related findings and well visits.
• Know the Tanner stages of development, both by pictures and text descriptions.
• Understand the preventative care and vaccine schedules for different ages.
• Know the physiological changes of adulthood and older adulthood.
• Review the developmental stages of infancy and young childhood.

Immune System (3-5%)

• Review the roles of different types of immune cells, including the activation and maturation of B and T cells, and the pathologies that can result from any immune deficiencies. 
• Know the four types of hypersensitivity reactions, including the physiology and examples of each.
• Grafts and types of rejection in regard to transplanted organs is also highly tested.
• Know the differences between primary and secondary immune responses and passive vs active immunity. 
• Though lower yield, this category may also include mechanisms of actions and side effects of immunosuppressive medications.
• Know the vaccine schedules!

 Blood & Lymphoreticular System (4-6%)

• Review the components of whole blood, blood types, Rh status, and transfusion reactions.
• You should also be able to interpret hematology labs
• It is useful to memorize the normal CBC numbers. This will allow you to move through the questions quicker and reduce test day anxiety. 
• Study different types of anemia, sickle cell, thalassemia, and various vitamin deficiencies, such as folate and B12. Make sure you know the pathophysiology of each and what blood smear findings you can expect to find. 
• You should be able to draw out the coagulation cascade and know the pathologies that result from various coagulation disorders. 
• Commonly used drugs that affect clotting should also be reviewed, including warfarin, heparin, aspirin, thrombin inhibitors, etc. 
• Know the differences amongst various types of leukemias and lymphomas, as well as their clinical presentations.  

Behavioral Health (6-8%)

• This is usually the most straightforward topic on Step 2 CK and often one that does not require extensive studying in comparison to some of the other subjects in this breakdown. 
• You should know the DSM-5 criteria for major physiological disorders, such as depression, anxiety, and bipolar disorder.
• The most difficult part about this section is often the mechanisms and side effects of medications.

Nervous System & Special Senses (6-8%)

• Know stroke presentations based on location and their medical management.
• Review different types of seizures and the antiepileptic drugs. 
• The findings in different types of dementia are highly tested. 
• Be able to workup and differentiate the causes of vertigo.
• Conditions such as ALS, MG, Lambert-Eaton, Guillain-Barre, and MS are high yield. Review presentation, treatment and complications!  
• Know the function of each cranial nerve.
• Be able to differentiate causes of headaches and how to treat them.

Musculoskeletal System/Skin & Subcutaneous Tissue (6-10%)

• Review common dislocations and fractures and what nerves or blood vessels can be affected.
• Pathologies of the hand such as carpal tunnel and trigger finger are commonly tested. 
• Know when to obtain imaging for back pain, ankle sprains and wrist fractures.
• Know the differences between the different types of myalgias and myositis such as PMR, dermatomyositis/polymyositis, statin-myopathy, etc. 
• Learn when a melanoma should be high on your differential.
• Become familiar with different physical exam maneuvers such as the straight leg raise, Tinel’s test, etc.
• Be able to differentiate the childhood viral illnesses based on skin rash presentation and onset.

Cardiovascular System (8-10%)

• Make sure to understand the anatomy and normal functions of the heart. 
• Be able to interpret and apply the Frank-Starling curve. 
• Be able to identify common arrhythmias through both a verbal description of an EKG and also by looking at an EKG.
• Familiarize yourself with illness scripts about coronary artery disease, ischemic heart disease, and acute coronary syndromes. 
• Differentiate between peripheral arterial disease and peripheral vascular disease 
• Know timeline and guidelines for AAA screening.
• Be able to differentiate antiarrhythmic medications and their side effect profiles.

Respiratory System (7-9%)

• One of the highest-yield topics is lung cancer, including the workup of a lung nodule, screening guidelines, and the different types of lung cancer.
• Memorize the Light’s criteria and be able to apply it for effusions.
• You should understand the Virchow’s triad, Wells’ Criteria, and the causes and physiology of pulmonary embolisms. 
• Other topics to review include asthma, COPD, and ARDS.
• Know the different types of coughs and their causes (croup vs. epiglottitis vs. bronchitis vs. pneumonia).
• Be able to explain lung mechanics and basic pathophysiology.
• Know the different classes of bronchodilators and treatments for COPD and asthma.

Gastrointestinal System (7-9%)

• Review esophageal and colon cancers, including their structure and causes.
• Be able to work up and diagnose the different causes of diarrhea, jaundice, dysphagia, malabsorption, and GI bleeding. 
• Know the difference between Crohn’s and UC.
• Be able to interpret hepatitis serologies.
• Know the screening timeline for colonoscopies based on age, polyp structure and biopsy findings.  
• Familiarize yourself with CT scans of the abdomen and be able to identify the different organs.
• Memorize the management of small and large bowel obstructions.
• Know the risk factors, presentation, workup, and treatment of C. diff colitis. 
• Differentiate the various treatments of constipation and diarrhea. 

Renal & Urinary System & Male Reproductive (4-6%)

• Review different parts of the nephron and understand their functions. 
• Know the common causes and treatments of hypo/hypernatremia, hypo/hyperkalemia, hypo/hypercalcemia
• Review acid-base disturbances. 
• Be able to differentiate amongst the causes of AKI and stages of CKD.
• Review common pediatric pathologies, such as posterior urethral valves and hypospadias. 
• Know the common presentations of renal, bladder, prostate, and testicular cancers and the treatments for each. 

Pregnancy, Childbirth & the Puerperium (4-6%)

• Commonly tested pathologies are ectopic pregnancy, different types of abortions, preeclampsia and eclampsia, postpartum hemorrhage.
• Memorize the different TORCH infections as well as prophylaxis, presentation, and treatments.
• Know common forms of birth control and their effectiveness.
• Familiarize yourself with pregnancy screening and timeline.
• Know the stages of labor and the evaluations performed during labor
• Review teratogenic medications and their fetal manifestations.

Female Reproductive System & Breast (4-6%)

• Review the different cervical, endometrial, ovarian and vaginal malignancies. 
• Know screening timeline for pap smears and co-testing for HPV. 
• Review the normal female pelvic and breast anatomy.
• Know how to evaluate and manage adnexal masses, vaginal bleeding, abnormal uterine bleeding, and primary/secondary amenorrhea
• Breast cancer screening, workup, and treatment will most likely show up on the test. 

Endocrine System (4-6%)

• Understand the hormonal pathways and commonly tested concepts. 
• Draw out and understand the HP axis, as well as the pathways of other hormones secreted by the anterior and posterior pituitary glands.
• Make sure you understand how negative feedback works in these pathways and the pathologies that result if it malfunctions. 
• Review the workup of a thyroid nodule, hyperthyroidism/hypoparathyroidism, and thyroid cancers’ key characteristics (histology, and clinical presentation).
• Understand the different types of hyperparathyroidism.
• MEN syndromes are very commonly tested.
• Know the presentation of pancreatic neuroendocrine tumors and which hormone is implicated.
• Review common pathologies of both pituitaries and the adrenal glands. 
• Review diabetes and HHNK heavily, including lab values, presentation, and treatment. 

 Multisystem Processes & Disorders (4-6%)

• This section focuses on multiple topics including immunology, inflammatory disorders, neoplasms, nutrition, toxins, acid-base disorders, abuse, genetic disorders, and adverse effects of drugs.
• The best way to prepare for this section is to be prepared for the other sections of the exam.

Biostatistics & Epidemiology / Population Health / Interpretation of Medical Literature

• It may be helpful to make a one-page sheet with important formulas that you can look over the morning of your test day. 
• Review formulas and applications of sensitivity/specificity, PPV/NPV, and formulas for relative risk, odds ratio, types of errors and their significance for the null hypothesis, and the p-value curve. 
• For population health, you should know different types of prevention, general vaccine schedules, and high-yield screening guidelines for colon/lung/cervical/breast cancers, AAA, HIV, smokers. 
• You should know the different types of clinical trials, the phases of a clinical trial, and how to interpret results in a study using the power and p-values. 

Social Sciences: Legal / Ethical Issues & Professionalism / Systems – based Practice and Patient Safety

• The best way to prepare for this is simply doing practice questions.
• Become familiar with ethical dilemmas from these practice questions and the best management for them.
• Apply professionalism behavior you’ve seen in real life to the exam.
• Think from the perspective of a test writer when answering patient safety questions. . 

Preparing for the USMLE Step 2 CK can feel overwhelming due to its breadth and depth, but breaking it down by subject and focusing on high-yield topics will help you make the most of your study time. Prioritize the systems with the largest exam weight and ensure you have a solid understanding of key concepts in physiology, pathology, and pharmacology for each category.

If you’re looking for personalized guidance to create an efficient study plan, master test-taking strategies, or deepen your understanding of challenging topics, Elite Medical Prep’s Step 2 tutors are here to support you every step of the way. Schedule a consultation and get started on your journey to success today!