There is no single medical cannabis dosage for epilepsy. The only cannabis-based epilepsy medicine with FDA approval is purified cannabidiol (CBD), and its label starts patients at about 2.5 mg per kilogram of body weight taken twice daily, then raises the amount to a maintenance range of 10 to 20 mg/kg per day. A prescribing doctor sets the exact dose, the pace of increase, and the ceiling for each patient.
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Why dosing varies from person to person
Seizure disorders differ, and so do bodies. A dose that controls seizures in a 60 kg teenager may cause heavy sleepiness in a 12 kg toddler.
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- Body weight, since CBD dosing is built on milligrams per kilogram.
- Seizure type and syndrome, including Dravet, Lennox-Gastaut, and tuberous sclerosis complex.
- Other anti-seizure drugs, which change how fast the liver clears CBD.
- Product strength and form, because a 10 mg/mL tincture and a 100 mg/mL oil are not interchangeable.
- THC content, which adds psychoactive effects and a different risk profile.
What the prescription CBD label says
The FDA-approved CBD oral solution is a 100 mg/mL liquid taken by mouth. Directions follow a weight-based titration instead of one fixed number.
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- Starting dose: about 2.5 mg/kg twice daily, or 5 mg/kg per day.
- Titration: increase about once a week, in steps the prescriber chooses.
- Maintenance: 10 mg/kg per day is common, and some patients move to 20 mg/kg per day.
- Upper limit: the label allows up to 25 mg/kg per day for one condition, tuberous sclerosis complex.
That schedule belongs to the prescription drug. It does not describe hemp-derived CBD sold in shops.
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How weight-based dosing math works
Weight-based dosing is multiplication and division. A 30 kg child at 2.5 mg/kg twice daily needs 75 mg per dose.
- Weigh the patient in kilograms (pounds divided by 2.2).
- Multiply weight by the mg/kg number from the prescriber: 30 x 2.5 = 75 mg.
- Check the bottle strength. With a 20 mg/mL oil, 75 divided by 20 gives 3.75 mL per dose.
- Measure with an oral syringe, not a kitchen spoon.
Kids grow, so the milligram amount needs a fresh look at each weight check.
What titration looks like week by week
Doctors start low and move slow because side effects show up before benefits do. A common pattern holds each new dose for one to two weeks before the next step.
- Week 1 to 2: starting dose, watching for sleepiness and stomach upset.
- Week 3 to 4: first increase if the patient tolerates the start.
- Week 5 and beyond: step up until seizures drop or side effects appear.
- Plateau: hold at the dose that gives the best trade-off between control and comfort.
Some families see a change in seizure counts within a few weeks. Others need months of slow changes to find a workable dose.
Side effects and drug interactions to watch
- Sleepiness, fatigue, and lower appetite are the most reported effects.
- Diarrhea and stomach upset show up in a share of patients.
- Liver enzyme rises are possible, which is why blood tests are part of the plan.
- CBD raises levels of clobazam's active metabolite, so that drug often needs a lower dose.
- Valproate plus CBD carries a higher chance of liver problems.
Bring a full medication list to every visit. Herbal supplements and other CBD products count on that list.
Is store-bought CBD the same thing?
No. Hemp CBD sold online or in shops is not an approved drug, and testing studies find bottles that hold more or less CBD than the label claims.
If you use a nonprescription product, choose one with a batch lab report that lists cannabinoid content and a passed test for pesticides and heavy metals. Show the report to your doctor so the dose in milligrams is clear.
What to track and share with your doctor
- Seizure count, duration, and type, logged by date.
- Dose in milligrams, time given, and any missed doses.
- Product name, strength, and lab report or batch number.
- Side effects, sleep, appetite, and mood.
- Blood test results and any changes to other seizure medicines.
Questions people ask about medical cannabis and epilepsy dosage
Can I start CBD for seizures without a doctor?
You can buy hemp CBD without a prescription, but you should not treat seizures on your own. Seizures can be dangerous, and CBD interacts with common anti-seizure drugs. Talk to a neurologist first.
How long does a dose change take to show results?
Effects on seizure frequency are measured over weeks, not hours. Doctors hold a new dose long enough to judge it before moving again.
Does CBD replace seizure medication?
In studies, CBD was added to existing treatment rather than swapped in. Stopping another drug without medical guidance can trigger longer or more severe seizures.
What is the top daily CBD dose for epilepsy?
The prescription label tops out at 25 mg/kg per day for one condition and 20 mg/kg per day for others. Higher amounts bring more side effects and need closer monitoring.
Is THC useful for seizures?
No cannabis product with THC is FDA approved for epilepsy. THC can cause intoxication, and its risk in children is a serious concern for most neurologists.
The short version
Dosing for epilepsy is a weight-based, doctor-led process that starts near 2.5 mg/kg twice daily and climbs to a range of 10 to 20 mg/kg per day. Small steps, clear records, and regular blood work matter more than any single number on a label.