Geriatric Dose Adjustment Calculator

Work out geriatric dose adjustment instantly with clear inputs, formula shown and shareable results.

About Geriatric Dose Adjustment Calculator

Applies the start low and go slow principle by combining an age-based reduction with a renal function reduction on the standard adult dose.

Formula

Combined reduction

Adjusted dose = standard dose x age factor (0.75 from 75 years, 0.5 from 85) x renal factor (0.75 for CrCl 30-49, 0.5 below 30)

Worked example

With the default values below, Geriatric Dose Adjustment Calculator returns Suggested starting dose of 5.63. Change any input above and every figure here is recalculated in your browser.

Inputs used

Standard adult doseaccepts 0.1–2,000 mg: 10 mg
Ageaccepts 60–110 years: 78 years
Creatinine clearanceaccepts 5–150 mL/min: 45 mL/min

Results

Suggested starting dose: 5.63 mg
Total reduction applied: 44%
Age factor: 0.75
Renal factor: 0.75

Step by step

1Values used
2Combined reduction
3Suggested starting dose= 5.63 mg
4Total reduction applied= 44
5Age factor= 0.75
6Renal factor= 0.75

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

Why reduce doses in older adults?

Lean mass, renal clearance and hepatic blood flow all fall, while sensitivity to sedatives and anticholinergics rises.

Should every drug be reduced?

No. Antibiotics and analgesics are often needed at full dose; the Beers and STOPP criteria identify the drugs that matter most.