About this gabapentin dosage calculator
Gabapentin is cleared from the body almost entirely by the kidneys without being metabolized, so its dosing depends directly on how well the kidneys filter blood. This calculator estimates that filtering rate - creatinine clearance (CrCl) - from age, weight, sex, and serum creatinine using the Cockcroft-Gault equation, then applies the FDA-labeled renal dosing table to show the total daily dose range and dosing frequency for that renal-function tier. It is a reference tool for the standard published formula, not a substitute for a prescriber's decision.
The Cockcroft-Gault formula
Estimated creatinine clearance is calculated as:
CrCl (mL/min) = [(140 - age) x weight(kg)] / (72 x serum creatinine (mg/dL)), x 0.85 if female
Age is in years and weight is actual body weight in kilograms. The 0.85 multiplier for female patients accounts for typically lower muscle mass, which produces less creatinine at a given filtration rate. This equation, from Cockcroft and Gault (1976), is the estimate the gabapentin prescribing information references for outpatients with stable renal function.
The FDA renal dosing table
Gabapentin's prescribing information sets total daily dose and dosing frequency by creatinine clearance band:
- CrCl 60 mL/min or above: 900-3600 mg/day, divided three times daily (TID).
- CrCl 30-59 mL/min: 400-1400 mg/day, divided twice daily (BID).
- CrCl 15-29 mL/min: 200-700 mg/day, once daily (QD).
- CrCl 15 mL/min or below: 100-300 mg/day, once daily, reduced further in proportion to clearance for values well below 15.
Patients on hemodialysis need a separate maintenance-plus-supplemental regimen (a post-dialysis supplemental dose after each 4-hour session) that this calculator does not compute; that schedule should come directly from the prescriber and dialysis team.
How the suggested per-dose split is built
The calculator clamps your entered target total daily dose to the FDA range for the calculated tier, then divides that clamped dose by the tier's dosing frequency (3 for TID, 2 for BID, 1 for QD) to show an illustrative per-dose amount. If your target was above or below the labeled range, the result notes that the dose was adjusted to fit the tier.
Important disclaimer
This tool performs the published renal-clearance and dose-banding arithmetic only. It does not account for the specific indication, titration schedule, drug interactions, or individual clinical judgment. Do not use it to start, stop, or change a gabapentin dose - any dosing decision should be made with a licensed prescriber or pharmacist.