Difficulty is personal, but a few HESI A2 sections consistently come up as the ones applicants struggle with most. Knowing why they are hard tells you where to spend your study time.
Math is the section most people name as hardest, not because the arithmetic is advanced but because it is applied and timed. Expect ratios, proportions, unit conversions, and dosage-style word problems that test whether you can set up the right calculation quickly. A basic on-screen calculator is provided, so the bottleneck is reading the problem correctly and choosing the method — not number-crunching. The fix is drilling the setups until they are automatic.
Chemistry combines vocabulary (atomic structure, bonds, the periodic table) with light calculation (balancing equations, moles, pH). Applicants who have not taken chemistry recently find the sheer number of linked concepts the hard part. Review the why behind each reaction rather than memorising isolated facts — understanding transfers, memorised lists fade.
A&P is hard because of breadth: directional terms, tissue and organ organisation, and the major body systems with their functions. There is a lot to hold in memory. A systems-level map — what each system does and how the pieces connect — beats memorising isolated structures, and it is what the questions usually reward.
Vocabulary feels easy until an unfamiliar word appears with no context to lean on. The section rewards a broad, steady vocabulary built over time, especially everyday and health-adjacent words. Learning words in sentences, not flashcard lists in isolation, is the efficient path.
Diagnose first: take a short mixed practice set and see where you lose the most points. Put the bulk of your time into your two weakest sections, keep the stronger ones warm with lighter review, and practise Math under a timer so pace stops being a surprise on test day.
Tap an answer to check it instantly. These 5 questions are free; the full timed exam has the rest.
1. Evaluate: 18 + 6 × (9 − 4) ÷ 3
Answer: B. Following the order of operations, 9 − 4 = 5, then 6 × 5 ÷ 3 = 10, and 18 + 10 = 28.
2. An atom has 17 protons, 18 neutrons, and 17 electrons. What is its mass number?
Answer: C. Mass number equals protons plus neutrons (17 + 18 = 35).
3. A nurse describes a wound on the patient's forearm as being located proximal to the wrist. Which statement best explains this term?
Answer: B. Proximal means nearer to the point of attachment to the trunk, so a site proximal to the wrist lies closer to the elbow.
4. A nurse reads in a patient's chart that a medication is contraindicated for the patient. What does this mean?
Answer: B. A contraindication is a condition or factor that makes a particular treatment or drug inadvisable because it could be harmful.
5. Which organelle is the primary site of ATP production through aerobic respiration in eukaryotic cells?
Answer: B. Mitochondria carry out the citric acid cycle and oxidative phosphorylation, generating most of the cell's ATP.
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Most applicants name Mathematics, because it is applied and timed — dosage-style word problems under time pressure. Chemistry, Anatomy & Physiology, and Vocabulary are the next most commonly cited, usually because of the volume of concepts and terminology to hold in memory.
The arithmetic itself is basic and a calculator is provided, but the section is timed and the problems are applied (ratios, conversions, dosage-style setups). The difficulty is speed and setup, which practice fixes.
Take a short diagnostic, then put most of your time into your two weakest sections. Practise Math under a timer, review Chemistry and A&P conceptually rather than by rote, and build Vocabulary in context over time.
Most applicants study over a few weeks rather than cramming. The right length depends on how far your weakest sections are from your program's target score — diagnose first, then focus.