Gentamicin Calculator NHS
This independent UK clinical calculation page explains adult gentamicin dosing calculations and monitoring. Gentamicin has a narrow therapeutic margin and NHS protocols differ between organisations, indications and patient groups, so this page deliberately does not generate a prescribing dose from a generic national formula.
Gentamicin dose arithmetic checker
Use this only to check the arithmetic of a dose already specified by your authorised local protocol or prescriber.
Do not prescribe from this result alone. Apply your local protocol’s dose cap, rounding, renal-function rules, interval, exclusions and serum-level monitoring.
Why there is no single NHS gentamicin dose
Current NHS guidance shows meaningful local variation. For example, University Hospitals Dorset uses an initial-dose calculator followed by a measured level 6–14 hours after the first dose to determine subsequent timing. A Norfolk and Norwich NHS guideline bases dose and interval on creatinine clearance and body weight, while other NHS protocols use different once-daily dose bands. Therefore copying one trust’s regimen and presenting it as a universal NHS dose would be unsafe.
Renal function and body weight matter
Gentamicin is cleared by the kidneys and accumulation can cause nephrotoxicity and ototoxicity. Protocols may require Cockcroft-Gault creatinine clearance and may specify actual, ideal or adjusted dosing weight depending on body size and the regimen. Use the exact definitions in your local antimicrobial policy.
Worked arithmetic example
If an authorised protocol has already specified 5 mg/kg and its required dosing weight is 60 kg, the arithmetic is 60 × 5 = 300 mg. This example checks multiplication only; it does not establish that 5 mg/kg, 60 kg, the interval or 300 mg is appropriate for a particular patient.
Monitoring and exclusions
NHS protocols commonly require serum gentamicin levels and renal-function monitoring. Separate regimens or specialist advice may be required for endocarditis, pregnancy, children, dialysis or renal replacement therapy, severe renal impairment and other high-risk situations. Always follow the current local guideline and antimicrobial/pharmacy advice.
Authoritative Sources
- University Hospitals Dorset NHS: Gentamicin Calculator
- Norfolk and Norwich University Hospitals NHS: Gentamicin Prescribing Guideline
- NHS Forth Valley: Gentamicin Treatment Dose Policy
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FAQs
Does this calculator prescribe a gentamicin dose?
No. It only checks mg/kg multiplication after an authorised protocol or clinician has supplied the dosing weight and mg/kg dose.
Why can the dose differ between NHS organisations?
Local antimicrobial protocols can use different regimens, dose bands, intervals, exclusions and monitoring methods.
Should eGFR or creatinine clearance be used?
Follow the specific local gentamicin protocol. Many medicine-dosing protocols use Cockcroft-Gault creatinine clearance rather than relying on laboratory eGFR alone.
Do gentamicin levels need monitoring?
Yes, therapeutic drug monitoring is an important part of NHS gentamicin treatment protocols; the required timing depends on the regimen.
Clinical safety disclaimer: This page is an educational arithmetic aid, not a prescribing system. Gentamicin can cause serious kidney and hearing toxicity. Never choose a dose, interval or monitoring plan from this page alone; use the current local NHS antimicrobial guideline and appropriate pharmacy, microbiology or specialist advice.