Study guide
1.3 Domain Weights and Study Strategy
NBCE Part I Basic Sciences Examination Exam
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1 Introduction & Exam Overview
1.1 Current Exam Facts 1.2 Format, Scoring, and Eligibility 1.3 Domain Weights and Study Strategy
2 General Anatomy: Surface, Bone, and Joints
2.1 Topographical Anatomy 2.2 Osteology of the Appendicular Skeleton 2.3 Arthrology and Syndesmology of the Appendicular Skeleton
3 General Anatomy: Muscle, Heart, and Lymph
3.1 Myology of the Appendicular Skeleton 3.2 Cardiovascular and Lymphatic Systems 3.3 Digestive System
4 General Anatomy: Respiratory, Urogenital, and Endocrine
4.1 Respiratory System 4.2 Urogenital System 4.3 Endocrine System Anatomy
5 Spinal Anatomy: Axial Skeleton
5.1 Osteology of the Axial Skeleton 5.2 Myology of the Axial Skeleton 5.3 Arthrology and Syndesmology of the Axial Skeleton
6 Spinal Anatomy: Neural Structures and Special Senses
6.1 Central Nervous System and Related Structures 6.2 Peripheral and Autonomic Nervous Systems 6.3 Organs of Special Senses
7 Physiology: Nerve, Muscle, and Circulation
7.1 Neurophysiology 7.2 Muscle Physiology 7.3 Cardiovascular Physiology
8 Physiology: Respiration, Kidney, and Gut
8.1 Respiratory Physiology 8.2 Body Fluids and Renal Physiology 8.3 Gastrointestinal Physiology
9 Physiology: Reproduction, Endocrine, and Exercise
9.1 Reproductive Physiology 9.2 Endocrine Physiology 9.3 Exercise and Sports Physiology
10 Chemistry: Macromolecules and Enzymes
10.1 Carbohydrates 10.2 Lipids 10.3 Proteins, Amino Acids, and Peptides 10.4 Enzymes
11 Chemistry: Hormones, Nucleic Acids, Vitamins, and Energetics
11.1 Hormones 11.2 Nucleotides and Nucleic Acids 11.3 Vitamins and Minerals 11.4 Biochemical Energetics
12 Pathology: Cellular, Genetic, and Immune Mechanisms
12.1 Fundamentals of Pathology 12.2 Genetic and Congenital Disorders 12.3 Disorders of the Immune System
13 Pathology: Environment, MSK, Nervous, and Organ Systems
13.1 Environmental and Nutritional Diseases 13.2 Disorders of the Musculoskeletal System 13.3 Disorders of the Nervous System 13.4 Diseases of the Organ Systems
14 Microbiology: Immunology, Bacteria, and Viruses
14.1 Immunology 14.2 Bacteria 14.3 Viruses and Prions
15 Microbiology: Fungi, Parasites, and Disease Control
15.1 Fungi 15.2 Parasites 15.3 Epidemiology and Disease Control
1.3 Domain Weights and Study Strategy
Key Takeaways Explain This Topic AI
Official Part I domain weights are General Anatomy 20%, Spinal Anatomy 22%, Physiology 18%, Chemistry 13%, Pathology 16%, and Microbiology 11%.
Session 1 (General Anatomy + Spinal Anatomy + Physiology) is 60% of the blueprint; Session 2 is 40%.
NBCE sample tests cost $15 per domain or $60 for all domains, use 50 items per domain, and report only an overall score without item-level keys.
The published first-time Part I part-level pass rate for January–July 2024 is 71%; do not cite 78% for Part I (that comparison figure is Part II).
A 180–280 hour total-study band is a planning range for this guide, not an NBCE-published hour requirement.
Last updated: August 2026
Official domain weights (learn these six numbers)
The Part I test plan publishes the percentage of the examination devoted to each domain. Those percentages are the only official “how much is this worth?” signal. NBCE does not publish how many of the 255 live items sit in each domain, so you cannot convert 22% into “56 questions” and treat that as a fact. Study by weight , not by an invented item count.
Domain Official weight Session What the weight means for calendar time
Spinal Anatomy 22% 1 Largest domain; only six numbered topics, so each topic must be taught and reviewed in depth
General Anatomy 20% 1 Nine numbered topics from surface anatomy through endocrine histology
Physiology 18% 1 Nine numbered topics, including reproductive and exercise physiology with no “skip this” clause
Pathology 16% 2 Mechanisms plus organ systems; musculoskeletal and nervous pathology are high-yield for chiropractic practice
Chemistry 13% 2 Eight numbered biochemistry topics from carbohydrates through oxidative phosphorylation
Microbiology 11% 2 Smallest domain, still six numbered topics including epidemiology; do not leave it for the last evening
- Session 1 total 60% 1 General Anatomy 20 + Spinal Anatomy 22 + Physiology 18
- Session 2 total 40% 2 Chemistry 13 + Pathology 16 + Microbiology 11
Session 1 is 60% of the blueprint. That is not a motivational slogan. If your study hours are split “evenly across six subjects,” you under-prepare the session that occupies most of the examination and that hits you while you are still cold. A practical allocation of a 200-hour planning block (the midpoint of the range below) would put about 120 hours into Session 1 domains and about 80 hours into Session 2 domains, then steal additional Spinal Anatomy time from the Session 1 pool because 22% sits on only six numbered headings.
Spinal Anatomy’s combination of highest weight and fewest numbered topics is the trap. “I already had neuroanatomy” is not a plan for osteology of C1/C2, ligament names, brachial and lumbosacral plexuses, tracts, and special senses. Later chapters in this guide therefore go long on axial osteology, myology, arthrology, CNS, PNS/ANS, and special senses. General Anatomy is close behind at 20% and is broader: if you only drill spine and skip the heart, gut, lung, and pelvis, you are studying a 22% exam that does not exist.
Microbiology at 11% is still large enough to fail a candidate who is otherwise strong in anatomy. Pathology at 16% rewards mechanism (cell injury, hypersensitivity type, thrombus versus embolus) rather than memorizing every eponym. Chemistry at 13% rewards pathways and vitamin cofactors that also leak into physiology and pathology items. Cross-link on purpose: glycogen storage belongs to chemistry and genetic pathology; hypersensitivity belongs to pathology and microbiology immunology.
How to use this guide with practice questions and NBCE samples
Work in three layers. Do not skip to timed tests before the blueprint is recognizable.
Layer 1 — Teach from the numbered test-plan topics. Each later chapter maps to official sub-topics (topographical anatomy, appendicular osteology, and so on). Read the section, say the tables aloud, and complete the in-section quizzes. Those quizzes are teaching checks, not a substitute for a 255-item sitting.
Layer 2 — Retrieve with mixed practice. Use /practice/nbce-part1 after a chapter, not only at the end of the week. Mixed anatomy-plus-physiology sets mimic Session 1 fatigue better than six separate subject silos. When you miss an item, return to the matching study-guide section rather than rereading an entire textbook chapter.
Layer 3 — Official NBCE sample tests for timing and stamina, not for an answer key. Sample tests are $15 per domain or $60 for all domains . Each domain sample is 50 items . You receive an overall score and you will not see which questions were answered correctly or incorrectly . That product is useful for clock feel and for a blunt “am I in the right zip code?” signal. It is a poor diagnostic map. Do not build an error log from items you cannot review. Do not treat 50 as the live per-domain count.
College lectures, NBCE’s reference text list , and this guide should agree on structures and mechanisms. If a commercial deck still teaches 300 items or $1,100, discard the logistics and keep only the science that matches the test plan.
Pass-rate context (71%, not 78%)
NBCE’s pass-rate page notes that domain-level rates were reported for January–July 2024 and part-level rates for August–December 2024. For comparison, it publishes the part-level rates from January–July 2024 as 71% for Part I and 78% for Part II , first-time examinees. Use 71% when you talk about Part I. Do not quote 78% as a Part I figure. Do not invent 2025 PDF percentages that NBCE has not put in that comparison footnote.
A 71% first-time part-level pass rate means roughly three in ten first-time candidates in that window did not pass at part level. That is not a reason to panic and not a reason to assume the exam is a formality because “everyone at my college passes.” NBCE also states that it does not predetermine pass percentages; rates vary by college and by year. Your job is to be in the passing group on the first eligible sitting, because failed attempts cost another $710, another 17-day lock, and another four-week score wait.
A 180–280 hour planning range (not an NBCE hour requirement)
NBCE does not publish a required number of study hours for Part I. The 180–280 hour band used here is a planning range for a candidate who has already completed the relevant college courses and needs a full re-study of six domains before a first part-level sitting. It is not a Board rule, not a guarantee, and not a substitute for the test plan. Candidates who finished biochemistry last week need fewer chemistry hours; candidates who have not seen spinal tracts since first year need more than the midpoint.
- Planning total Rough calendar if you have 12 weeks Notes
- 180 hours About 15 hours/week Minimum honest re-study if course mastery is recent and high
- 230 hours About 19 hours/week Mid/upper band if anatomy is rusty or chemistry was a struggle
- 280 hours About 23 hours/week Use when several domains were weakly learned the first time
Inside whatever total you choose, keep Session 1 near 60% of hours, keep Spinal Anatomy heavier than a naive “one-sixth of time” split, and leave a final 10–14 days for mixed practice plus one NBCE sample sitting that you treat as a dress rehearsal. Sleep and a valid ID the morning of the exam are part of performance; a 375 is a scaled standard, not a reward for overnight cramming of 255 facts.
If you remember only three strategy sentences: weight hours to 20/22/18/13/16/11 , respect Session 1 as 60% , and use practice questions plus unscored samples without pretending 50 live items per domain exist. Then open the next chapter and start topographical anatomy rather than rereading this overview.