Medical Math

Basic math accuracy underpins all clinical calculations.

• Master fractions, decimals, percentages, and ratios/proportions.
• Rounding and estimation help catch unreasonable answers.
• Order of operations and unit tracking prevent errors.
• Understanding place value is critical for reading doses correctly.

Health care uses several measurement systems that must be converted accurately.

• The metric system (g, mg, mcg, L, mL) is the medical standard.
• Know household (teaspoon, cup) and apothecary units and how they convert.
• Common conversions: 1 g = 1000 mg; 1 L = 1000 mL; 1 kg ≈ 2.2 lb; 1 inch = 2.54 cm.
• Temperature conversion between Fahrenheit and Celsius is often required.

Dosage and IV math must be exact to keep patients safe.

• The basic dosage formula: desired ÷ have × quantity.
• Weight-based dosing (mg/kg) is common in pediatrics.
• IV flow rate uses drop factor: (volume × drop factor) ÷ time in minutes = gtt/min.
• Always double-check calculations to avoid dangerous errors.

Preparing solutions requires understanding concentration.

• Concentration can be expressed as percent, ratio, or mg/mL.
• A dilution lowers concentration by adding solvent; C₁V₁ = C₂V₂ relates the values.
• Solute is what's dissolved; solvent is what dissolves it.
• Accurate mixing matters for medications, lab reagents, and cleaning agents.

Clinicians must read and use numeric health data correctly.

• Read charts, graphs, and tables of vital signs and lab values.
• Understand intake and output (I&O) records and fluid balance.
• Interpret lab reference ranges to flag abnormal results.
• Convert and compare units when reviewing medical records.