Wellbutrin (bupropion) comes in three formulations, each with different tablet strengths, dosing frequencies, and daily limits. The most commonly prescribed version, Wellbutrin XL, starts at 150 mg once daily and is typically increased to 300 mg once daily. The specific dose depends on which formulation you’re taking and what condition it’s being used to treat.
Three Formulations, Three Schedules
The key difference between Wellbutrin’s three versions is how the medication releases into your body, which determines how often you take it.
- Wellbutrin IR (immediate-release): Taken two to three times per day, with doses spaced at least six hours apart. Individual tablets should not exceed 150 mg.
- Wellbutrin SR (sustained-release): Taken twice per day, with at least eight hours between doses. Available in 100 mg, 150 mg, and 200 mg tablets.
- Wellbutrin XL (extended-release): Taken once per day in the morning. Available in 150 mg and 300 mg tablets.
Wellbutrin XL is the most widely prescribed because of its once-daily convenience. All three formulations deliver the same active ingredient; they simply differ in how quickly your body absorbs it.
Doses for Depression
For major depressive disorder, the FDA-approved starting dose of Wellbutrin XL is 150 mg once daily in the morning. After four days at that dose, it can be increased to the target dose of 300 mg once daily. Most people being treated for depression end up on 300 mg per day.
The absolute ceiling for Wellbutrin XL is 450 mg per day. The standard prescribing label states the dose should not exceed 300 mg once daily for most patients, but 450 mg is sometimes used when a lower dose hasn’t provided enough relief. That upper limit exists primarily because of seizure risk: at 450 mg per day or less, seizures occur in roughly 0.35% to 0.44% of patients. At 600 mg per day, the seizure rate jumps to about ten times that level.
For the SR formulation, treatment typically starts at 150 mg once in the morning, then increases to 150 mg twice daily. The maximum is 400 mg per day (200 mg per dose). The IR version follows a similar pattern but splits the daily amount across three doses.
Doses for Seasonal Affective Disorder
Wellbutrin XL is the only formulation approved to prevent seasonal depression. The starting dose is 150 mg once daily in the morning, and the maximum is 300 mg once daily. The timing matters: you start taking it in early autumn, before symptoms typically begin, and continue through winter into early spring. The dose is then tapered down before stopping, rather than discontinued abruptly.
Doses for Smoking Cessation
When bupropion is prescribed for quitting smoking, it’s sold under the brand name Zyban rather than Wellbutrin, though the medication is identical. The schedule begins with 150 mg once daily for the first three days, then increases to 150 mg twice daily with at least eight hours between doses. The maximum is 300 mg per day.
Treatment runs for 7 to 12 weeks. You start taking it one to two weeks before your planned quit date, giving the medication time to build up in your system. If you haven’t quit after 12 weeks, continuing the same course is unlikely to work, and a different approach is usually considered. Some people who do quit successfully stay on it longer to reduce the risk of relapse.
Dose Adjustments for Liver or Kidney Problems
Your liver does most of the work breaking down bupropion, so liver impairment changes how the drug accumulates in your body. People with mild to moderate liver problems typically start at the lowest available dose, with increases guided by how well they tolerate it. For severe liver impairment, the dose should not exceed 150 mg per day, or in some cases 150 mg every other day, because the drug and its byproducts can build up to levels that raise the risk of side effects like insomnia, dry mouth, and seizures.
Kidney impairment creates a similar concern. Reduced kidney function slows the clearance of bupropion’s active byproducts, so a lower dose or less frequent dosing is typically used.
Dosing in Older Adults
Older adults tend to do well on lower doses. Clinical reports show that doses in the range of 75 to 225 mg per day produce fewer side effects in elderly patients while maintaining the same effectiveness seen at higher doses in younger adults. The concern with higher doses in this group is that bupropion’s active byproducts can accumulate, particularly if kidney or liver function has declined with age. This accumulation raises the risk of seizures and other neurological side effects.
Why Doses Are Increased Gradually
Regardless of formulation or condition, bupropion is always started at a lower dose and increased over several days. This gradual approach exists specifically to reduce seizure risk. The brain needs time to adjust to the medication, and jumping straight to a full dose increases the chance of overstimulation. The same logic applies to spacing out doses during the day for the IR and SR versions: taking two doses too close together creates a spike in blood levels that mimics a higher dose than intended.
If you miss a dose, skip it and take the next one at its regular time. Never double up to compensate, since the temporary spike in drug levels is exactly the kind of situation the dosing rules are designed to prevent.