Gabapentin Dosage Calculator
Gabapentin Dosage Calculator
Age in years (minimum 3 for epilepsy, 12 for other indications)
Required for pediatric weight-based dosing
Optional — enter CrCl or eGFR (mL/min) for renal dose adjustment
Select the available tablet/capsule strength to calculate pill count
Enter Patient Details
Select an indication and enter patient information to see the gabapentin dosing recommendation, titration schedule, and renal adjustments.
Important
This calculator is provided for general information only and is not medical advice, diagnosis, or treatment. Results are estimates based on population averages and cannot account for your individual circumstances. Speak to a qualified healthcare professional before acting on anything you read here.
Indication-based dosing with renal adjustment and titration schedule
Gabapentin (brand name Neurontin) is an anticonvulsant and analgesic medication used to treat a wide range of conditions, from epilepsy and postherpetic neuralgia to neuropathic pain, restless leg syndrome, and several off-label indications. Because gabapentin dosing depends heavily on the clinical indication, patient age, body weight (for pediatric patients), and kidney function, calculating the right dose and titration schedule can be complex and error-prone without a reliable reference tool. This Gabapentin Dosage Calculator provides indication-specific dosing recommendations based on published clinical guidelines and FDA-approved prescribing information. Whether you are a healthcare professional reviewing dosing options, a student studying pharmacology, or a patient wanting to understand your prescribed regimen, this tool helps you understand the standard dosing principles for gabapentin across eight indications. For adult patients, the calculator supports all major indications: epilepsy and partial-onset seizures (FDA-approved), postherpetic neuralgia (FDA-approved), neuropathic pain, diabetic peripheral neuropathy, restless leg syndrome, anxiety, fibromyalgia, and alcohol withdrawal — the last six being off-label uses. Each indication has its own titration schedule, maintenance dose range, and maximum daily dose hard cap. The tool clearly flags whether the selected indication carries FDA approval or is an off-label use, helping users understand the regulatory and evidence context. For pediatric patients aged 3 to 11 years, gabapentin is FDA-approved only for adjunctive therapy of partial-onset seizures. Pediatric dosing uses weight-based calculations: a starting dose of 10–15 mg/kg/day divided into three doses, titrating to an effective maintenance dose of 40 mg/kg/day (ages 3–4) or 25–35 mg/kg/day (ages 5–11), with a hard maximum of 50 mg/kg/day. The calculator automatically routes to pediatric logic when the age group is set to pediatric and a body weight is entered. Renal function adjustment is one of the most critical aspects of safe gabapentin prescribing. Gabapentin is almost entirely renally excreted, meaning any reduction in kidney function directly prolongs its half-life and requires dose reduction. In patients with normal renal function (CrCl ≥ 60 mL/min), gabapentin has a half-life of 5–7 hours. In patients with severely impaired function (CrCl < 30 mL/min), the half-life can extend to approximately 52 hours — creating serious accumulation risk if the standard dose is continued. The calculator applies the established four-band adjustment table: CrCl ≥ 60 (standard TID dosing), 30–59 (BID dosing with reduced daily total), 15–29 (once-daily), and less than 15 mL/min (reduced once-daily). For patients on hemodialysis, a supplemental post-dialysis dose of 125–350 mg per session is recommended. The formulation picker lets you select the available gabapentin capsule or tablet strength (100 mg, 300 mg, or 400 mg capsules; 600 mg or 800 mg tablets) and instantly see how many units are needed per dose and per day. This is especially useful for patients self-managing their prescriptions or caregivers counting pills for a daily schedule. The titration schedule table shows a day-by-day escalation plan — Day 1, Day 2, and Day 3 onwards — so users can see exactly how the dose should ramp up to the maintenance range. A CSS safety bar visually indicates where the calculated maintenance dose sits relative to the maximum allowed daily dose, providing an at-a-glance check for potential over-dosing risk. As with all medication calculators, this tool is for educational and reference purposes only. All dosing decisions must be made by a licensed healthcare professional who can account for the patient's full clinical picture, comorbidities, drug interactions, and individual response to therapy.
Understanding Gabapentin Dosing
What Is Gabapentin?
Gabapentin is a gamma-aminobutyric acid (GABA) analogue that was originally developed as an anticonvulsant. Despite its name, it does not act directly on GABA receptors. Instead, it binds to the alpha-2-delta subunit of voltage-gated calcium channels in the central nervous system, reducing the release of excitatory neurotransmitters such as glutamate, norepinephrine, and substance P. This mechanism explains its effectiveness in neuropathic pain conditions. Gabapentin is FDA-approved for partial-onset seizures (adjunctive therapy) and postherpetic neuralgia. It is also widely used off-label for conditions including restless leg syndrome, generalized anxiety disorder, fibromyalgia, diabetic peripheral neuropathy, and alcohol withdrawal management. It is available in immediate-release capsules (100 mg, 300 mg, 400 mg), tablets (600 mg, 800 mg), and an extended-release formulation (Gralise). The immediate-release forms are the basis for all dosing in this calculator.
How Is Gabapentin Dosing Calculated?
Adult gabapentin dosing is indication-specific and typically follows a three-day titration protocol before reaching the maintenance range. For postherpetic neuralgia: 300 mg on Day 1, 600 mg on Day 2, then 900 mg/day (300 mg TID) from Day 3, titrating up to 1800 mg/day (600 mg TID) over subsequent weeks. For epilepsy: start at 900 mg/day (300 mg TID) and titrate to 900–1800 mg/day maintenance; maximum 3600 mg/day. Pediatric epilepsy uses weight-based dosing: starting dose 10–15 mg/kg/day in 3 divided doses, with effective maintenance of 40 mg/kg/day (ages 3–4) or 25–35 mg/kg/day (ages 5–11). Renal adjustment uses the Cockcroft-Gault framework: CrCl ≥ 60 mL/min uses standard TID dosing; CrCl 30–59 switches to BID with reduced totals; CrCl 15–29 uses once-daily dosing; CrCl < 15 uses further-reduced once-daily dosing. Pill count is calculated as total daily dose divided by tablet/capsule strength.
Why Correct Dosing Matters
Getting gabapentin dosing right matters because both underdosing and overdosing carry significant clinical consequences. Underdosing fails to achieve therapeutic serum concentrations, leaving seizures uncontrolled or neuropathic pain inadequately managed. Overdosing — particularly in patients with renal impairment — can cause severe sedation, ataxia (loss of coordination), dizziness, respiratory depression, and, in overdose situations, potentially fatal outcomes. The renal adjustment is especially important because gabapentin does not undergo hepatic metabolism; it is eliminated almost entirely via glomerular filtration. When renal function declines, gabapentin accumulates unless the dose is reduced proportionally. For patients on hemodialysis, the standard half-life no longer applies because dialysis removes gabapentin efficiently, requiring a supplemental post-session dose to maintain therapeutic levels. Correct titration also matters: too rapid an escalation increases adverse effects; too slow may delay pain or seizure control.
Limitations of This Calculator
This calculator provides general dosing guidance based on published clinical guidelines and FDA prescribing information. It cannot account for every clinical variable that a prescribing physician considers: concurrent medications (particularly CNS depressants, opioids, or other anticonvulsants), the patient's complete medical history, organ function beyond renal status (e.g., hepatic conditions affecting albumin and drug binding), individual pharmacokinetic variability, or the patient's subjective response to the drug. Pediatric dosing is FDA-approved only for partial-onset seizures adjunctive therapy in children aged 3 and older — off-label pediatric use is not addressed. The renal dosing table uses CrCl bands from GlobalRPH and published clinical literature; exact thresholds may differ from your institution's protocols. Gabapentin is a controlled substance in some US states and countries, and prescribing regulations vary. Always consult a licensed healthcare professional before initiating, adjusting, or discontinuing gabapentin therapy.
How to Use This Calculator
Select Age Group and Indication
Choose whether the patient is an adult (12 years or older) or pediatric (ages 3–11). Then select the clinical indication being treated — this determines the dosing protocol, titration schedule, and maximum daily dose. FDA-approved indications are clearly labeled.
Enter Patient Details
For adults, enter the patient's age. For pediatric patients, enter both age and body weight (you can toggle between kg and lb). Optionally enter the patient's Creatinine Clearance (CrCl) or eGFR in mL/min — this enables renal dose adjustment. Toggle the hemodialysis switch if the patient is dialysis-dependent.
Select Formulation
Choose the available gabapentin formulation from the dropdown — 100 mg, 300 mg, or 400 mg capsules, or 600 mg / 800 mg tablets. The calculator will use this to display the number of pills or capsules required per dose and per day.
Review Results and Print
Review the maintenance dose range, titration schedule, dose per administration, frequency, and maximum daily dose. If renal function was entered, the renal-adjusted dose is shown separately. Use the Print button to save or print the dosing summary to share with your healthcare provider.
Frequently Asked Questions
What is the standard starting dose of gabapentin for adults?
The standard starting dose for most adult indications follows a three-day titration protocol. On Day 1, the patient takes 300 mg once. On Day 2, this increases to 300 mg twice daily (600 mg total). From Day 3 onwards, the dose reaches 300 mg three times daily (900 mg/day), which is the typical minimum effective dose for conditions like postherpetic neuralgia and neuropathic pain. For epilepsy, some protocols start at 300 mg TID immediately. The dose may then be slowly increased over weeks based on clinical response and tolerability, up to the indication-specific maximum — typically 3600 mg/day for epilepsy and neuropathic pain.
How does kidney disease affect gabapentin dosing?
Kidney disease has a profound effect on gabapentin dosing because gabapentin is eliminated almost entirely through the kidneys via glomerular filtration without hepatic metabolism. In patients with normal renal function (CrCl ≥ 60 mL/min), gabapentin has a half-life of 5–7 hours and is dosed three times daily. As kidney function declines, the drug accumulates: CrCl 30–59 requires switching to twice-daily dosing with a reduced daily total (400–1400 mg/day); CrCl 15–29 requires once-daily dosing (200–700 mg/day); CrCl < 15 requires further reduced once-daily dosing (100–300 mg/day). In severely impaired patients (CrCl < 30), the half-life can extend to approximately 52 hours, making accumulation a serious safety concern.
Does gabapentin require a supplemental dose after hemodialysis?
Yes. Hemodialysis efficiently removes gabapentin from the bloodstream because gabapentin is a small, water-soluble molecule with minimal protein binding. Each 4-hour dialysis session removes a significant fraction of the drug. Patients on chronic hemodialysis typically receive a maintenance dose of 200–300 mg per day between sessions (adjusted based on residual renal function), plus a supplemental post-dialysis dose of 125–350 mg after each session. This supplemental dose replaces the drug removed during dialysis and ensures therapeutic levels are maintained. The exact supplemental dose should be determined by a nephrologist or clinical pharmacist familiar with the patient's dialysis parameters.
Is gabapentin safe for children?
Gabapentin is FDA-approved as adjunctive therapy for partial-onset seizures in children aged 3 years and older. Pediatric dosing is weight-based: starting at 10–15 mg/kg/day divided into three doses, then titrating to an effective maintenance dose of 40 mg/kg/day for children aged 3–4 years, or 25–35 mg/kg/day for children aged 5–11 years, with a maximum of 50 mg/kg/day. For other indications, gabapentin use in children is off-label and lacks the same level of clinical evidence as adult use. The capsule formulation's safety profile in children under 12 with renal impairment has not been well studied. Any gabapentin use in pediatric patients should be supervised by a pediatric neurologist or pediatrician.
Which gabapentin indications are FDA-approved versus off-label?
Gabapentin has only two FDA-approved indications: (1) adjunctive therapy for partial-onset seizures in adults and pediatric patients aged 3 and older, and (2) management of postherpetic neuralgia in adults. All other uses are off-label, including neuropathic pain (general), diabetic peripheral neuropathy, restless leg syndrome, anxiety and generalized anxiety disorder, fibromyalgia, and alcohol withdrawal management. Off-label does not mean ineffective or unsafe — many off-label uses are supported by clinical evidence and are considered standard of care — but it does mean the FDA has not formally reviewed and approved the drug for that specific purpose. This calculator clearly flags FDA-approved versus off-label status for each indication.
What is the maximum dose of gabapentin per day?
The maximum daily dose of gabapentin depends on the indication and the patient's renal function. For epilepsy and most neuropathic pain indications, the generally cited maximum is 3600 mg/day (1200 mg three times daily). For fibromyalgia, the maximum is typically cited as 2400 mg/day. For restless leg syndrome, doses rarely exceed 1800 mg/day. These maximums apply to patients with normal renal function (CrCl ≥ 60 mL/min). In patients with renal impairment, the maximum is proportionally reduced according to the CrCl band. Exceeding the maximum without medical supervision significantly increases the risk of adverse effects including severe sedation, respiratory depression, and toxicity — especially when combined with opioids or other CNS depressants.