🧠 Before You Calculate Anything
Most dosage errors are reading errors, not math errors. This section trains you to slow down, understand exactly what is being asked, and align your units correctly. Slow is smooth, smooth is safe.
Step 1
What Exactly is the Question Asking Me?
Scroll straight to the very last sentence of the problem before looking at a single number. Find the final requested unit (e.g., mL/hr, tablets, mg/dose). Write it down. Never start calculating until you know your destination.
Micro-Exercise
The provider orders heparin 25,000 units in 250 mL D5W to infuse at 18 units/kg/hr. The patient weighs 80 kg. Calculate the infusion rate in mL/hr.
Step 2 · The Unit Alignment Rule
Apples to Apples, Tomatoes to Tomatoes
Every unit on the top must have a matching unit on the bottom. If the doctor orders mcg but the pharmacy provides mg, stop. You must convert to make them match before calculating.
Conversion Operation Example mcg → mg Divide by 1,000 500 mcg = 0.5 mg mg → mcg Multiply by 1,000 0.5 mg = 500 mcg g → mg Multiply by 1,000 1 g = 1,000 mg Step 3 · The Weight Trap
Is the Weight in the Right Unit?
Medication orders standardly use Kilograms (kg), but clinical charts love to give you patient weights in Pounds (lbs). Your absolute first move must always be: Pounds ÷ 2.2 = Kilograms (rounded to the nearest tenth).
⚠️ Common Trap
Plugging lbs directly into a mg/kg formula makes your dose 2.2× too high.
Example: 154 lbs ÷ 2.2 = 70.0 kgStep 4 · The Hidden Question
Total Daily Dose vs. Per-Dose Amount
Watch for phrases like 'in divided doses'. If an order says 'Amoxicillin 600 mg/day in divided doses TID', you must recognize that TID means 3 times a day. If the question asks for the amount 'per dose', the answer is 200 mg, NOT 600 mg.
Wrong
600 mg
Daily total given at once
Per-dose
200 mg
600 ÷ 3 (TID) = 200
Step 5 · The Bedside Reality Check
Does Your Answer Make Clinical Sense?
Before submitting any answer, ask yourself these real-world screening questions:
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Would I actually give this much to a real human? If you get an answer requiring 15 tablets or 500 mL for a single dose, your decimal point is misplaced.
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IV infusion rates over 999 mL/hr are a massive clinical red flag — re-check your conversion immediately.
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Ready to begin the numbers?
Confirm you've internalized the 5-step ritual. This unlocks the Core Diagnostic Test and all 5 progressive levels.