FREE COMLEX Level 1 Study Guide 2026: Sciences + OMM

This free COMLEX Level 1 study guide walks through the highest-yield content the COMLEX-USA Level 1 exam tests — the foundational biomedical sciences and the distinctive osteopathic principles and practice (OMM) — organized by the disciplines you actually study.^[1]

It is interactive, not a wall of text: every discipline has worked clinical reasoning, comparison tables, labeled diagrams, and built-in flashcards — taught to the level a future DO is expected to reach to progress toward licensure.

Read it discipline by discipline, then round out your prep with our practice questions and flashcards. The exam has 320 questions in two four-hour sessions and is reported Pass/Fail — with no numeric score since May 2022.^[3]

COMLEX Level 1 Exam Snapshot

Most of the exam is foundational science. Competency Domain 1, Application of Knowledge, is about 60% of the items, and that is where anatomy, physiology, biochemistry, microbiology, pathology, and pharmacology are tested. The distinctive osteopathic content — OPP and OMM — is about 12% as its own domain, but osteopathic thinking is woven throughout.^[1]

Weight your study toward the sciences, then make the osteopathic points (which are highly memorizable) easy wins.

The osteopathic domains (OPP/OMT plus Osteopathic Patient Care) together make up roughly 18% of the exam — the content that has no equivalent on the USMLE Step 1.^[1] Because these points are rule-based and memorizable (autonomic levels, technique definitions, the tenets and models), they are some of the most reliable points on the test.

How COMLEX Level 1 Is Built (Two Dimensions)

COMLEX Level 1 is built from the NBOME blueprint, which scores every question on two dimensions at once.^[1] Dimension 1 is the seven Competency Domains for Osteopathic Medical Licensure — what competency the item measures.

Dimension 2 is the ten Clinical Presentations— the body system or presentation the item is about. A single question might be “Application of Knowledge” (Dimension 1) and “Circulatory & Hematologic Systems” (Dimension 2). The foundational sciences are not a separate weighted axis; they are tested through these clinical presentations.

COMLEX Level 1 is reported Pass/Fail only. Since May 10, 2022 the NBOME no longer releases a three-digit numeric score; the historical minimum passing standard was anchored at a scaled score of 400, but candidates now receive only a Pass/Fail outcome plus a formative performance profile by content area. There is no penalty for guessing.^[3]

This guide groups the foundational sciences into six discipline modules (anatomy, physiology, biochemistry, microbiology/immunology, pathology, and pharmacology), then devotes two modules to the osteopathic content — the principles and structural diagnosis (OPP), and the manipulative techniques plus the competency framework (OMT, biostatistics, professionalism).^[1]

Anatomy & Embryology

Anatomy is a foundational pillar of Application of Knowledge (Domain 1, ~60%) and is especially high-yield on COMLEX because it links directly to osteopathic structural diagnosis.^[1] Focus on clinically testable nerve lesions, the brachial and lumbosacral plexuses, and the neuroanatomy of the autonomic outflow.

Gross & Neuroanatomy Essentials

Know the brachial plexus (roots C5–T1) and the classic injuries: Erb–Duchenne palsy (upper trunk, C5–C6, the “waiter’s tip”) and Klumpke palsy (lower trunk, C8–T1, claw hand).

Master peripheral nerve lesions tied to fractures: the radial nerve with a mid-shaft humeral fracture (wrist drop), the axillary nerve with a surgical-neck fracture or shoulder dislocation, and the common peroneal nerve with a fibular neck injury (foot drop). For the cranial nerves, the trigeminal nerve (CN V) carries facial sensation and the muscles of mastication, and a brainstem lesion can cross findings (ipsilateral face, contralateral body).

Nerve Lesions & Clinical Anatomy

Horner syndrome (ptosis, miosis, anhidrosis) results from interruption of the cervical sympathetic chain and is a recurring crossover with the autonomics you will study in the osteopathic modules. Recognize compression syndromes (Saturday-night radial palsy, carpal tunnel of the median nerve) and the dermatomal/myotomal patterns that localize a spinal level. Anatomy on COMLEX rewards localization — given a deficit, name the nerve, root, or tract.

Physiology

Physiology threads through nearly every clinical presentation. The highest-yield blocks are cardiovascular electrophysiology, renal handling and acid–base, and the autonomic nervous system — the last of which is the bridge into the osteopathic modules.^[1]

Cardiovascular & the Action Potential

Know the cardiac action potential: phase 0 is rapid Na⁺ influx (in ventricular myocytes), phase 2 is the plateau from Ca²⁺ influx balancing K⁺ efflux, and phase 3 is repolarization from K⁺ efflux. In the SA node, phase 4 spontaneous depolarization (the “funny” Na⁺ current and Ca²⁺) sets the heart rate, and the high resting parasympathetic (vagal) tone keeps the intrinsic rate below the node’s natural pace.

Carotid sinus massage raises vagal tone and can slow AV conduction. Match these mechanisms to the antiarrhythmic classes you study in pharmacology.

Renal, Acid–Base & Autonomics

The proximal convoluted tubule reabsorbs the largest fraction of filtered sodium and water; the juxtaglomerular apparatus secretes renin in response to low perfusion, driving the renin–angiotensin–aldosterone system. For acid–base problems, use the anion gap and expected-compensation rules: a thiazide plus vomiting causes a hypokalemic, contraction metabolic alkalosis, while chronic COPD causes a respiratory acidosis the kidneys compensate by retaining bicarbonate.

The autonomic nervous system is two divisions — sympathetic (thoracolumbar, T1–L2) and parasympathetic (craniosacral) — the exact framework the osteopathic modules build on.

Biochemistry & Genetics

Biochemistry on COMLEX favors metabolism (glycolysis, the citric acid cycle, oxidative phosphorylation), enzyme kinetics, and the inherited enzyme deficiencies. Learn the rate-limiting steps and the consequences of blocking each pathway.^[7]

Metabolism & Enzyme Kinetics

In glycolysis, phosphofructokinase-1 is the committed, rate-limiting step. The net of glycolysis is one glucose to two pyruvate, with a net gain of 2 ATP and 2 NADH. One turn of the citric acid cycle produces 3 NADH, 1 FADH₂, 1 GTP, and 2 CO₂; the reducing equivalents then drive oxidative phosphorylation, which produces most of the cell’s ATP.

For enzyme kinetics, Km is the substrate concentration at half of Vmax — a low Km means high affinity. A competitive inhibitor raises the apparent Km without changing Vmax; a non-competitive inhibitor lowers Vmax without changing Km.

Genetics & Inherited Disease

Know the high-yield enzyme deficiencies and their cellular consequences — for example, a pyruvate kinase deficiency impairs the last ATP-generating step of glycolysis and causes a hemolytic anemia in red cells, which depend entirely on glycolysis for energy. Recognize inheritance patterns and chromosomal lesions (such as the Philadelphia chromosome, the BCR-ABL fusion of chronic myeloid leukemia) at a mechanism level. The unifying skill is connecting a missing enzyme to the substrate that accumulates and the product that is lost.

Microbiology & Immunology

Microbiology rewards a systematic identification framework, and immunology centers on the four hypersensitivity types and the players of innate vs adaptive defense.^[8]

Bacteria, Viruses & Fungi

Start every bacterial question with the Gram stain and morphology, then branch by catalase, coagulase, and hemolysis. Gram-positive cocci split into Staphylococcus (catalase-positive: coagulase-positive S. aureus vs coagulase-negative S. epidermidis/saprophyticus) and Streptococcus (catalase-negative, sorted by hemolysis).

Gram-negative organisms carry an LPS outer membrane (endotoxin), driving septic shock. Know the motile gram-positive rod Listeria monocytogenes and the resistant Pseudomonas aeruginosa. Connect organisms to the classic clinical presentation rather than memorizing in isolation.

Immune Defense & Hypersensitivity

The four hypersensitivity types (mnemonic ACID) are constantly tested: Type I is immediate, IgE-mediated (anaphylaxis, atopy); Type II is antibody-mediated cytotoxicity (autoimmune hemolytic anemia, Goodpasture); Type III is immune-complex (serum sickness, the Arthus reaction, lupus); and Type IV is delayed, T-cell mediated (the PPD/TB test, contact dermatitis, transplant rejection).

The complement system bridges innate and adaptive immunity — C3a and C5a are anaphylatoxins and C5a is a potent neutrophil chemoattractant. A second exposure to an allergen causes a far stronger Type I reaction because memory IgE is already bound to mast cells.

Pathology

Pathology is the “why” behind the clinical presentations — the mechanisms of cell injury, inflammation, repair, and neoplasia. It is one of the densest sources of COMLEX questions.^[9]

Cell Injury, Inflammation & Repair

Distinguish the two forms of cell death: apoptosis is a programmed, energy-dependent process affecting single cells without inflammation, while necrosis is unregulated death of groups of cells that triggers inflammation.

The five cardinal signs of acute inflammation are redness, heat, swelling, pain, and loss of function, produced by vasodilation, increased vascular permeability, and leukocyte (neutrophil) recruitment. Acute inflammation is neutrophil-dominated and short-lived; chronic inflammation features lymphocytes, plasma cells, and macrophages with tissue destruction and repair (fibrosis, angiogenesis).

Neoplasia & the Genetics of Cancer

The single defining feature of malignancy is metastasis — the spread of tumor cells to a distant, non-adjacent site. Malignant tumors are poorly differentiated, grow rapidly with an infiltrative margin, and invade; benign tumors are well differentiated, slow, and encapsulated.

To metastasize, cancer cells must acquire capabilities (invasion, angiogenesis, evasion of apoptosis). Carcinomas (epithelial) spread first via lymphatics; sarcomas (mesenchymal) spread first hematogenously. Recognize the role of oncogenes and tumor-suppressor loss (the Philadelphia chromosome BCR-ABL fusion in CML).

Pharmacology

Pharmacology questions test mechanisms, drug classes, kinetics, and adverse effects. The autonomic and cardiovascular drugs are the densest, and they pair directly with the physiology you have just studied.^[11]

Autonomic & Cardiovascular Drugs

Map drugs to receptors: alpha-1 agonism causes vasoconstriction (raising blood pressure); beta-1 agonism increases heart rate and contractility (dobutamine in heart failure); and muscarinic agonists like bethanechol stimulate the bladder and gut. For arrhythmias, the Vaughan-Williams classes are: I (Na⁺ channel blockers), II (beta-blockers), III (K⁺ channel blockers such as amiodarone and sotalol), and IV (non-dihydropyridine Ca²⁺ channel blockers such as verapamil and diltiazem, useful for rate control). Beta-blockers reduce post-MI mortality partly through their antiarrhythmic effect.

Pharmacokinetics & Drug Classes

Distinguish first-order elimination (a constant fraction removed per unit time; constant half-life — most drugs) from zero-order elimination (a constant amount removed regardless of concentration — ethanol, phenytoin, high-dose aspirin), where small dose increases cause disproportionate, dangerous rises in plasma level. Know that statins competitively inhibit HMG-CoA reductase, and that probenecid blocks renal tubular secretion of penicillin to raise its levels. The unifying skill is predicting effect, duration, and toxicity from the receptor and the elimination kinetics.

Osteopathic Principles & Practice

This is the content that makes COMLEX COMLEX. Osteopathic Principles, Practice & Manipulative Treatment is Competency Domain 1 (~12%), and the osteopathic tenets are described by the NBOME as foundational to every other domain.^[1] The points here are highly memorizable — make them guaranteed.

The Tenets, Models & Somatic Dysfunction

Memorize the four tenets (the body is a unit; it is capable of self-regulation and self-healing; structure and function are reciprocally interrelated; rational treatment is based on these three) and the five models of care (biomechanical, respiratory–circulatory, neurological, metabolic–energy, behavioral).^[5]

Somatic dysfunction is diagnosed by the TART findings (Tissue texture change, Asymmetry, Restriction, Tenderness) — any one is sufficient. Name the dysfunction by where the segment moves freely: a Type II is FRS or ERS (flexion/extension, rotation, sidebending to the same side, single segment), while a Type I is neutral with rotation and sidebending to opposite sides across a group.

Autonomics, Chapman’s Points & Reflexes

The autonomic levels are the single most-tested OMM fact set. All sympathetic preganglionic fibers arise from T1–L2; the parasympathetic system is craniosacral (CN III, VII, IX, X and S2–S4). A viscerosomatic reflex produces paraspinal tissue changes at the organ’s sympathetic level — so a finding at T1–T5 suggests the heart, T5–T9 the foregut (stomach, liver, gallbladder), and T10–T11 the kidney.

Chapman’s points are tender neurolymphatic nodules at predictable locations that point to a specific organ. The osteopathic concept of facilitation explains how a segment can perpetuate heightened sympathetic output.

OMT, Behavioral Science & the Competencies

The final module covers osteopathic manipulative treatment (Osteopathic Patient Care & Procedural Skills, ~6%) plus the remaining competency domains — Practice-Based Learning (biostatistics and evidence-based medicine), Communication, Professionalism, and Systems-Based Practice.^[1]

OMT Techniques & Their Indications

Classify each technique as direct (engages the restrictive barrier) or indirect (moves away from it, into ease).

Muscle energy is direct: the patient actively contracts against the physician’s counterforce, then post-isometric relaxation lets the barrier be re-engaged. Counterstrain is indirect: position the patient into ease, away from the tender point, and hold ~90 seconds. HVLA is a direct, quick thrust through the barrier (with an audible cavitation).

Myofascial release can be direct or indirect; cranial osteopathy palpates the primary respiratory mechanism. Know the contraindications — HVLA is contraindicated where there is bony instability, such as metastatic cancer to the spine or Down syndrome with atlantoaxial instability.

Biostatistics & the Competency Domains

Practice-Based Learning (~4%) is where biostatistics lives. Know sensitivity (true-positive rate — a negative result on a sensitive test rules OUT, “SnNout”) and specificity (true-negative rate — a positive on a specific test rules IN, “SpPin”).

Predictive values depend on prevalence (PPV falls as prevalence falls), while likelihood ratios do not. Understand relative risk vs the odds ratio, number needed to treat, p-values and confidence intervals, and the strengths of cohort vs case-control vs randomized designs.

The remaining domains — Communication, Professionalism, and Systems-Based Practice — test patient-centered communication, ethics and informed consent, and how care is delivered within the health system.

How to Use This Study Guide

Work through the guide one discipline at a time. After each one, check it off in the contents to raise your exam-readiness score, then drill the same content in our free practice questions and flashcards — active recall and timed practice are what move knowledge into exam-day performance.

• Spend most time on the sciences. Application of Knowledge is ~60% of the exam — anatomy, physiology, biochemistry, microbiology, pathology, and pharmacology are where most points live.
• Make OMM your guaranteed points. The autonomic levels, the tenets and five models, Fryette’s types, and the OMT technique definitions are pure recall — bank them.
• Learn mechanisms, not lists. For each topic, know the one fact that drives the answer (the rate-limiting enzyme, the receptor, the sympathetic level, the defining feature of malignancy).
• Read for the task. A topic can be asked as diagnosis, mechanism, best next step, drug, or OMM finding — identify what the stem is actually asking.
• Pace by session. Two 4-hour sessions for 320 questions is roughly 90 seconds each; answer, flag the hard ones, and never leave a blank (no guessing penalty).
• Then prove it. When a discipline feels solid, confirm with our practice questions — build a comfortable margin before exam day.

Common concepts COMLEX Level 1 candidates study and get asked — each answered briefly and backed by an official source (NBOME, AOA, NIH, CDC, or NCI). Tap any card to test yourself.

COMLEX Level 1 Glossary

Key COMLEX Level 1 terms in one place. Hover any dotted term throughout the guide for its definition; the full list is below.

COMLEX-USA Level 1

The first of the three-level Comprehensive Osteopathic Medical Licensing Examination from the NBOME — a 320-question exam that osteopathic medical students take after their first year to progress toward DO licensure.

NBOME

The National Board of Osteopathic Medical Examiners — the body that develops and administers the COMLEX-USA examination series and sets the passing standard.

DO

Doctor of Osteopathic Medicine — a fully licensed physician trained at a COCA-accredited college of osteopathic medicine, equivalent in practice rights to an MD, with additional training in osteopathic principles and OMM.

OPP

Osteopathic Principles and Practice — the philosophy and clinical application of osteopathic medicine, including the four tenets, the five models of care, and structural diagnosis.

OMM

Osteopathic Manipulative Medicine — the diagnosis and hands-on treatment (OMT) of somatic dysfunction; Competency Domain 1 (OPP/OMT) is ~12% of COMLEX Level 1.

OMT

Osteopathic Manipulative Treatment — the hands-on techniques (HVLA, muscle energy, counterstrain, myofascial release, cranial, and others) a DO uses to treat somatic dysfunction.

somatic dysfunction

Impaired or altered function of related components of the somatic (body framework) system — skeletal, arthrodial, and myofascial structures and their vascular, lymphatic, and neural elements — diagnosed by the TART findings.

TART

The four palpatory criteria for somatic dysfunction: Tissue texture change, Asymmetry, Restriction of motion, and Tenderness. Any one is sufficient to diagnose somatic dysfunction.

viscerosomatic reflex

A somatic (musculoskeletal) finding — tissue texture change, tenderness, restriction — produced by afferent input from a diseased internal organ entering the cord at the organ's sympathetic level.

Chapman's points

Small, tender, smooth fascial nodules (neurolymphatic reflex points) at predictable anterior and posterior locations, used in osteopathic diagnosis to point to a specific visceral problem.

Fryette's principles

Three laws describing coupled spinal motion: in neutral, sidebending and rotation are to opposite sides (Type I); in flexion/extension, they are to the same side (Type II); and motion in one plane affects motion in the others.

Type I somatic dysfunction

Neutral-mechanics dysfunction: the spine is neutral, sidebending and rotation occur to opposite sides, and a group of vertebrae is involved — classically a chronic, compensatory curve.

Type II somatic dysfunction

Non-neutral dysfunction: the spine is flexed or extended, sidebending and rotation occur to the same side, usually a single vertebra — often acute and symptomatic (named FRS or ERS).

muscle energy

A direct OMT technique in which the patient actively contracts a muscle against the physician's precise counterforce; post-isometric relaxation then allows the restrictive barrier to be engaged further.

counterstrain

An indirect OMT technique that resolves a tender point by passively positioning the patient into a position of ease (away from the barrier) and holding it, classically for about 90 seconds.

HVLA

High-velocity, low-amplitude — a direct OMT technique using a quick, short thrust through the restrictive barrier, often producing an audible release (cavitation).

sympathetic nervous system

The thoracolumbar division of the autonomic nervous system; all preganglionic cell bodies arise from spinal levels T1 through L2 in the lateral horn — the basis of viscerosomatic level mapping.

parasympathetic nervous system

The craniosacral division of the autonomic nervous system, arising from cranial nerves III, VII, IX, and X and sacral levels S2–S4; the vagus (CN X) supplies viscera to the splenic flexure.

Michaelis-Menten Km

The substrate concentration at which an enzyme runs at half its maximum velocity; a low Km indicates high substrate affinity. On a Lineweaver-Burk plot the x-intercept is −1/Km.

Krebs cycle

The citric acid cycle — one turn yields 3 NADH, 1 FADH₂, 1 GTP, and 2 CO₂; its reducing equivalents feed the electron transport chain for oxidative phosphorylation.

Gram stain

A staining method that sorts bacteria by cell-wall structure: gram-positive (thick peptidoglycan) stain purple; gram-negative (thin peptidoglycan plus an LPS outer membrane) stain pink.

hypersensitivity reactions

Four immune reaction types — I immediate/IgE, II antibody-mediated cytotoxic, III immune-complex, IV delayed/T-cell — recalled by the mnemonic ACID.

first-order elimination

Drug elimination in which a constant fraction is removed per unit time, so the rate is proportional to concentration and the half-life is constant — the kinetics of most drugs.

zero-order elimination

Drug elimination in which a constant amount is removed per unit time regardless of concentration (saturated enzymes), as with ethanol, phenytoin, and high-dose aspirin.

metastasis

The spread of malignant cells from a primary tumor to a distant, non-adjacent site via blood, lymph, or body cavities — the single defining feature of malignancy.

facilitation (osteopathic)

A state in which a spinal cord segment maintains a lowered threshold to firing, perpetuating heightened sympathetic output to the related viscera and somatic tissues.

sensitivity

The proportion of people WITH a disease who test positive (true-positive rate); a highly sensitive test, when negative, helps rule a disease OUT (SnNout).

specificity

The proportion of people WITHOUT a disease who test negative (true-negative rate); a highly specific test, when positive, helps rule a disease IN (SpPin).

COMLEX Level 1 Study Guide FAQ

References

1. 1.National Board of Osteopathic Medical Examiners (NBOME). “COMLEX-USA Level 1 — Blueprint & Competencies.” nbome.org. ↑
2. 2.National Board of Osteopathic Medical Examiners (NBOME). “COMLEX-USA Bulletin of Information 2025–2026.” nbome.org. ↑
3. 3.National Board of Osteopathic Medical Examiners (NBOME). “COMLEX-USA Level 1 to Eliminate Numeric Scores.” nbome.org. ↑
4. 4.National Board of Osteopathic Medical Examiners (NBOME). “Enhancements to COMLEX-USA Exams in 2026, 2027.” nbome.org. ↑
5. 5.American Osteopathic Association (AOA). “What Is Osteopathic Medicine?.” osteopathic.org. ↑
6. 6.U.S. National Library of Medicine (MedlinePlus). “Autonomic Nervous System.” medlineplus.gov. ↑
7. 7.National Institutes of Health (NIH). “Biochemistry, Citric Acid Cycle.” ncbi.nlm.nih.gov. ↑
8. 8.National Institutes of Health (NIH). “Hypersensitivity Reactions.” ncbi.nlm.nih.gov. ↑
9. 9.National Institutes of Health (NIH). “Acute Inflammatory Response.” ncbi.nlm.nih.gov. ↑
10. 10.National Cancer Institute (NCI). “Metastasis (NCI Dictionary of Cancer Terms).” cancer.gov. ↑
11. 11.National Institutes of Health (NIH). “Pharmacokinetics.” ncbi.nlm.nih.gov. ↑
12. 101.National Board of Osteopathic Medical Examiners (NBOME). “COMLEX-USA Level 1 Blueprint & Competencies.” nbome.org, accessed 19 June 2026. ↑
13. 102.U.S. National Library of Medicine (MedlinePlus). “Enzymes (overview).” medlineplus.gov, accessed 19 June 2026. ↑
14. 103.Centers for Disease Control and Prevention (CDC). “About Antimicrobial Resistance.” cdc.gov, accessed 19 June 2026. ↑
15. 104.National Institute of Neurological Disorders and Stroke (NINDS). “Autonomic Dysfunction.” ninds.nih.gov, accessed 19 June 2026. ↑

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