Why the Numbers Matter
Two of the eight NCLEX-PN categories are built on numbers. Pharmacological Therapies (10–16% of scored items) covers dosage calculation, therapeutic drug levels and the effects you must recognise; Reduction of Risk Potential (9–15%) covers laboratory values, vital signs and the complications those values predict. Together they are a fifth to a third of your exam, and a large share of them are impossible without a memorised reference range: an item that says "potassium 6.1 mEq/L" only makes sense if you know the ceiling is 5.0.
This guide is the reference list — the values the exam expects from memory, the critical results that trigger a report, the arterial blood gas method, and each dosage-calculation formula worked through in the format the exam uses. Read it once for understanding, then drill it: our free NCLEX-PN practice questions include lab-value and calculation items with the working shown in every explanation.
The Numbers Behind These Items
| Item | NCLEX-PN (2026 test plan) |
|---|---|
| Pharmacological Therapies weight | 10–16% of scored items |
| Reduction of Risk Potential weight | 9–15% of scored items |
| Combined, on the 52 content items of a minimum-length exam | About 10–16 questions |
| Calculation item format | Fill-in-the-blank: you type a number, no options; the item states the unit and the rounding |
| Calculator | An on-screen calculator is provided; no personal calculator |
| Where dosage calculation sits in the test plan | Pharmacological Therapies — "Dosage Calculation" and "Medication Administration" |
| Where lab values sit | Reduction of Risk Potential — "Laboratory Values" and "Changes/Abnormalities in Vital Signs" |
Electrolytes and Renal Values
| Test | Normal range | What the exam pairs it with |
|---|---|---|
| Sodium (Na⁺) | 135–145 mEq/L | Low: confusion, seizures, fluid overload or SIADH. High: thirst, dehydration, restricted water. |
| Potassium (K⁺) | 3.5–5.0 mEq/L | Low: loop diuretics, vomiting, muscle weakness, flat T waves, digoxin toxicity risk. High: renal failure, potassium-sparing diuretics, peaked T waves, dysrhythmia. |
| Calcium (Ca²⁺) | 8.5–10.5 mg/dL | Low: tetany, positive Chvostek and Trousseau signs after thyroid surgery. High: kidney stones, constipation, immobility. |
| Magnesium (Mg²⁺) | 1.5–2.5 mEq/L | Low: tremor, hyperreflexia, alcohol use disorder. High: magnesium sulfate infusions — lost patellar reflex, respiratory depression. |
| Chloride (Cl⁻) | 95–105 mEq/L | Moves with sodium; rarely tested alone. |
| Phosphorus | 2.5–4.5 mg/dL | Inverse to calcium; high in renal failure. |
| Blood urea nitrogen (BUN) | 10–20 mg/dL | Rises with dehydration and renal failure; the ratio to creatinine tells you which. |
| Creatinine | 0.6–1.2 mg/dL | The kidney number: a rise means reduced glomerular filtration. Check before contrast, metformin, aminoglycosides. |
| Glucose, fasting | 70–100 mg/dL | Under 70: hypoglycaemia — treat with 15 g of fast carbohydrate and recheck in 15 minutes. Over 126 fasting on two occasions defines diabetes. |
| Haemoglobin A1c | Below 5.7% normal; below 7% is the usual goal in diabetes | Three-month average; the value that tells you whether the regimen is working. |
Blood Counts and Coagulation
| Test | Normal range | What to know |
|---|---|---|
| Haemoglobin | Women 12–16 g/dL · Men 14–18 g/dL | Below 7–8 g/dL usually prompts transfusion consideration; report a fall of 2 g/dL or more. |
| Haematocrit | Women 36–48% · Men 42–52% | Roughly three times the haemoglobin; rises with dehydration. |
| White blood cells | 5,000–10,000/mm³ | Above 10,000: infection or inflammation. Below 5,000: neutropenia risk — protective precautions, no fresh flowers or raw food. |
| Platelets | 150,000–400,000/mm³ | Below 150,000 is thrombocytopenia; below 50,000, bleeding precautions (soft toothbrush, no IM injections, no razors). |
| Prothrombin time (PT) | 11–13.5 seconds | Warfarin monitoring; INR is the standardised version. |
| INR | 0.8–1.1 off anticoagulants · 2–3 on warfarin (2.5–3.5 for mechanical valves) | Above 4–5: hold warfarin, report; antidote is vitamin K. |
| aPTT | 30–40 seconds · 1.5–2.5 × control (about 45–90 s) on heparin | Above the therapeutic range: hold the infusion, report; antidote is protamine sulfate. |
Therapeutic Drug Levels
A handful of narrow-therapeutic-index drugs appear again and again, because the nurse's job is to hold the dose and report when the level is high.
| Drug | Therapeutic range | Toxicity looks like |
|---|---|---|
| Digoxin | 0.5–2.0 ng/mL | Anorexia, nausea, visual changes (yellow-green halos), bradycardia. Hold for an apical pulse under 60. |
| Lithium | 0.6–1.2 mEq/L | Coarse tremor, vomiting, diarrhoea, confusion. Toxicity is likelier with dehydration and low sodium. |
| Phenytoin | 10–20 mcg/mL | Nystagmus, ataxia, slurred speech; gingival hyperplasia with long-term use. |
| Theophylline | 10–20 mcg/mL | Tachycardia, tremor, seizures. |
| Magnesium sulfate (obstetric infusion) | 4–7 mEq/L | Lost deep tendon reflexes, respirations under 12, urine output under 30 mL/h. Antidote: calcium gluconate. |
| Vancomycin trough | 10–20 mcg/mL | Nephrotoxicity and ototoxicity; draw the trough just before the next dose. |
Arterial Blood Gases in Three Steps
| Value | Normal | Meaning |
|---|---|---|
| pH | 7.35–7.45 | Below 7.35 acidosis; above 7.45 alkalosis |
| PaCO₂ | 35–45 mm Hg | The respiratory value: high CO₂ is acid |
| HCO₃⁻ | 22–26 mEq/L | The metabolic value: high bicarbonate is base |
| PaO₂ | 80–100 mm Hg | Oxygenation; under 60 is respiratory failure |
| SaO₂ | 95–100% | Saturation |
- pH first — acidosis or alkalosis.
- Find the cause with ROME — Respiratory Opposite: if PaCO₂ moves opposite to the pH (pH down, CO₂ up), the problem is respiratory. Metabolic Equal: if HCO₃⁻ moves the same way as the pH (pH down, bicarbonate down), it is metabolic.
- Check compensation — if the other value has moved to pull the pH back toward normal, the body is compensating (partially while the pH is still abnormal, fully once it is back in range).
Example: pH 7.30, PaCO₂ 52, HCO₃⁻ 25. Acidosis; CO₂ is high and opposite to the pH, so respiratory acidosis; bicarbonate is normal, so uncompensated. Typical client: opioid over-sedation or a COPD exacerbation — the nursing action is to improve ventilation, not to give bicarbonate.
Dosage Calculations: Every Formula With a Worked Example
Calculation items are fill-in-the-blank. The stem tells you the unit to answer in and how to round — usually to the nearest whole number for drops and tablets, to one decimal place for millilitres. Round only at the end, and never round an intermediate weight or concentration.
1. Desired over have
Dose ordered ÷ dose on hand × quantity = amount to give. Order: amoxicillin 500 mg. On hand: 250 mg/5 mL suspension. 500 ÷ 250 × 5 = 10 mL.
2. Unit conversions you must know
| Conversion | Value |
|---|---|
| 1 g | 1,000 mg |
| 1 mg | 1,000 mcg |
| 1 kg | 2.2 lb |
| 1 L | 1,000 mL |
| 1 tsp / 1 tbsp / 1 oz | 5 mL / 15 mL / 30 mL |
| 1 grain (gr) | 60 mg (some references use 65) |
Order: 0.25 mg. On hand: 125 mcg tablets. Convert first: 0.25 mg = 250 mcg. 250 ÷ 125 = 2 tablets.
3. Weight-based doses
Convert pounds to kilograms by dividing by 2.2, then multiply by the mg/kg. A child weighs 44 lb; the order is 10 mg/kg. 44 ÷ 2.2 = 20 kg; 20 × 10 = 200 mg. If the item then asks for millilitres of a 100 mg/5 mL suspension: 200 ÷ 100 × 5 = 10 mL.
4. IV rate in mL per hour (infusion pump)
Total volume ÷ total hours. 1,000 mL over 8 hours = 125 mL/h. For minutes: mL ÷ minutes × 60. An antibiotic of 100 mL over 30 minutes = 100 ÷ 30 × 60 = 200 mL/h.
5. Drops per minute (gravity set)
Volume (mL) × drop factor (gtt/mL) ÷ time (minutes). 500 mL over 4 hours with a 15 gtt/mL set: 500 × 15 ÷ 240 = 31.25 → 31 gtt/min. Drops are always rounded to a whole number; you cannot count a quarter of a drop.
6. Dose per hour from a running infusion
Heparin 25,000 units in 500 mL is infusing at 20 mL/h. Concentration: 25,000 ÷ 500 = 50 units/mL. Rate: 50 × 20 = 1,000 units/h. The reverse — an order of 800 units/h — is 800 ÷ 50 = 16 mL/h.
7. Insulin and other units
Insulin is drawn only in an insulin syringe marked in units; no calculation is needed, and the exam item that asks you to convert units to millilitres for insulin is testing whether you know not to. Heparin doses in units use the concentration on the vial: 5,000 units ordered from a 10,000 units/mL vial = 0.5 mL.
The Values That Mean "Report Now"
- Potassium under 3.0 or over 6.0 mEq/L; sodium under 125 or over 155 mEq/L.
- Glucose under 50 or over 400 mg/dL; any glucose under 70 with symptoms.
- Platelets under 50,000/mm³ or a haemoglobin under 7 g/dL — or a fall of 2 g/dL from the last value.
- INR above 4 on warfarin; aPTT above 90 seconds on heparin; any active bleeding on either.
- A digoxin level above 2.0 ng/mL, a lithium level above 1.5 mEq/L, or a phenytoin level above 20 mcg/mL.
- A urine output under 30 mL/h for two consecutive hours; a rising creatinine in a client on nephrotoxic drugs or contrast.
- A pH outside 7.30–7.50 or a PaO₂ under 60 mm Hg.
The practical nurse's action for each is the same three moves: hold the medication that caused or worsens it where one exists, keep the client safe, and report to the registered nurse or provider with the value, the time and the client's symptoms.
Frequently Asked Questions
Do I get a calculator on the NCLEX-PN?
Yes, an on-screen calculator is built into the exam for calculation items. You may not bring your own, and you get an erasable note board for working.
How do I round dosage-calculation answers on the NCLEX?
Follow the instruction in the item — it always states the unit and the rounding, such as "record your answer using one decimal place". Round only the final answer, never an intermediate step, and round drops per minute and tablets to whole numbers when the item does not say otherwise.
Which lab values are most tested on the NCLEX-PN?
Potassium, sodium, glucose, creatinine, haemoglobin, platelets, INR and aPTT, plus the therapeutic ranges for digoxin, lithium and phenytoin. Those cover the large majority of lab-value items in the Reduction of Risk Potential and Pharmacological Therapies categories.
Are lab ranges the same on every NCLEX item?
No. Laboratories differ slightly, so Next Generation case studies print the reference range next to each result. Use the printed range when it is there; memorised ranges are for stand-alone items that give only the value.
How many calculation questions are on the NCLEX-PN?
NCSBN does not publish a count. Dosage calculation is one topic inside Pharmacological Therapies (10–16% of the exam), so expect a few fill-in-the-blank calculations on a minimum-length exam rather than a whole section of them.
Sources
- 2026 NCLEX-PN Test Plan, National Council of State Boards of Nursing — the Pharmacological Therapies and Reduction of Risk Potential content lists and their weights.
- NCLEX candidate materials at NCLEX.com — the on-screen calculator, fill-in-the-blank calculation items and the rounding instruction printed in each item.
- Reference ranges and therapeutic drug levels are the values taught in standard practical-nursing pharmacology and medical-surgical texts; laboratories publish their own ranges and Next Generation items display them.
- The worked examples are QuizCram's own and do not reproduce NCSBN items.
