Formulas
| Problem | Formula | Example |
|---|---|---|
| Tablets or liquid | D ÷ H × Q | 500 mg ÷ 250 mg × 5 mL = 10 mL |
| Weight-based | mg/kg × (lb ÷ 2.2) | 10 mg/kg × 20 kg = 200 mg |
| Pump rate | mL ÷ hours | 1,000 mL ÷ 8 h = 125 mL/hr |
| Gravity drip | mL × gtt/mL ÷ minutes | 1,000 × 15 ÷ 480 = 31 gtt/min |
Habits that prevent errors
- Convert to the same unit before dividing (mg with mg, mcg with mcg; 1 mg = 1,000 mcg).
- Round only at the end, and to what can actually be measured or counted.
- Ask whether the answer makes sense: ten tablets for one dose usually means a unit mistake.
Try 5 NCLEX-RN practice questions
A client with atrial fibrillation is prescribed warfarin (Coumadin). The nurse is reviewing the medication administration record. Which laboratory value should the nurse monitor most closely?
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A. International normalized ratio (INR) Warfarin is an anticoagulant that requires INR monitoring to ensure therapeutic effectiveness and prevent bleeding complications. The target INR for atrial fibrillation is typically 2.0 to 3.0. Hemoglobin and platelet count are not specific to warfarin therapy, and WBC is unrelated to anticoagulation monitoring.
A nurse is caring for a client with a central venous catheter. Which intervention is the MOST effective in preventing catheter-related bloodstream infections?
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B. Performing hand hygiene before and after accessing the line Hand hygiene before and after accessing any vascular access device is the single most effective measure to prevent catheter-related bloodstream infections. Changing dressings every 72 hours is not evidence-based, antibiotic ointment increases infection risk, and prophylactic antibiotics promote resistance.
A charge nurse observes that a newly licensed nurse is administering medications without scanning the barcode on the client's wristband. What is the best initial action?
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A. Provide immediate feedback and demonstrate proper scanning technique The charge nurse should provide immediate feedback to correct the behavior and prevent harm. Filing an incident report or notifying the manager before addressing the issue directly is premature. The priority is correcting the unsafe practice in real time.
A community health nurse is planning a smoking cessation program. According to the Health Promotion model, which action should the nurse take FIRST?
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D. Conduct a needs assessment to identify barriers to quitting A needs assessment is the foundation of any health promotion program. The nurse must first identify the specific barriers, readiness to change, and resources available in the community before implementing interventions.
A postoperative client reports severe pain rated 9 out of 10. The client has a physician order for morphine 2 mg IV every 4 hours as needed. What should the nurse do FIRST?
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A. Administer the morphine and document the pain rating With severe pain rated 9/10 and an existing order, the nurse should administer the medication promptly and document. Reassessment occurs after administration. Non-pharmacological methods are adjuncts, not replacements for severe acute pain.
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Common questions
Desired over have times quantity: D ÷ H × Q. If the order is 500 mg and the medication comes as 250 mg in 5 mL, give 500 ÷ 250 × 5 = 10 mL.
Convert the weight to kilograms (pounds ÷ 2.2), then multiply by the ordered dose per kilogram. 10 mg/kg for a 44 lb child is 10 × 20 = 200 mg.
Divide the total volume by the hours. 1,000 mL over 8 hours is 125 mL/hr.
Volume in mL × the tubing's drop factor (gtt/mL) ÷ time in minutes. 1,000 mL over 8 hours with 15 gtt/mL tubing is 1,000 × 15 ÷ 480 = 31.25, rounded to 31 gtt/min.
No. It is for learning the math. Real doses follow the prescriber's order, your facility's policy, the drug reference and an independent double check where required.
Sources, checked 2026-10-29: OpenStax, Pharmacology for Nurses, chapter on medication calculations; NCSBN, NCLEX test plans (pharmacological and parenteral therapies). For study only, not for patient care. QuizCram is not affiliated with the agencies or standards bodies named here.
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