Wellbutrin Side Effects: Timeline From Week 1 to Month 3

It’s day five on Wellbutrin, and you’re wide awake at 1 a.m. with a mouth that feels like cotton. You want to know two things: is this normal, and will it pass? The answer depends on the side effect, and the evidence is stronger for some than others.

Bupropion, the drug in Wellbutrin, works differently from SSRIs. The Wellbutrin XL prescribing information describes it as a relatively weak blocker of norepinephrine and dopamine reuptake with no effect on serotonin, and in controlled studies it increased motor activity and agitation. That activating quality shows up in its most common early complaints, like trouble sleeping and feeling on edge. Your body reaches steady blood levels within about 8 days, and doses rise with precision, one step at a time, because seizure risk climbs with dose.

The standard way to size up Wellbutrin’s side effects is the label’s placebo-controlled trial data, which compare each effect on the drug with a placebo. A seven-trial pooled analysis of nearly 2,000 patients found bupropion matched SSRIs on remission while causing less sexual dysfunction and sleepiness, though more dry mouth. The results are real, and the science is well established.

But a label tells you how often a side effect happens, not when it starts or how long it lasts, and at Siggy we’d rather show you the timeline the evidence supports, including where it runs out. This guide walks through week 1, the first dose increase, and months 2 and 3, using a large trial analysis that tracked when side effects began and ended. Knowing what tends to pass and what needs a call keeps each decision grounded in evidence.

What This Page Covers

• What Are the Most Common Wellbutrin Side Effects?
• Week 1: Starting at 150 mg
• Weeks 2 to 4: The Dose Step Up
• Months 2 and 3: What Fades and What Lingers
• Why Seizure Threshold Rules Shape the Timeline
• Which Side Effects Need a Call Right Away?
• How to Make Side Effects Easier to Live With

What Are the Most Common Wellbutrin Side Effects?

The Wellbutrin XL Medication Guide lists the most common side effects as trouble sleeping, stuffy nose, dry mouth, dizziness, feeling anxious, nausea, constipation, and joint aches.

In depression trials of the sustained-release (SR) form, which the label says delivers similar drug levels to Wellbutrin XL, these stood out at 300 mg a day compared with placebo:

• Dry mouth: 17% versus 7%
• Nausea: 13% versus 8%
• Insomnia: 11% versus 6%
• Tremor: 6% versus 1%
• Sweating and ringing in the ears: 6% each, versus 2%
• Rash: 5% versus 1%

Headache was nearly as common on placebo (23% versus 26%). Several effects climbed with dose: at 400 mg, insomnia reached 16%, dizziness 11%, and agitation 9%. About 9% of people stopped because of side effects at 300 mg and 11% at 400 mg, compared with 4% on placebo.

Wellbutrin XL’s own seasonal depression trials, lasting up to about 6 months, showed a similar pattern, led by dry mouth (26% versus 15%), headache (34% versus 26%), insomnia (20% versus 13%), and constipation (9% versus 2%).

Week 1: Starting at 150 mg

Wellbutrin XL usually starts at 150 mg each morning, and the first week is when insomnia tends to begin.

The best timing data come from an analysis of the EAGLES trial, which followed 2,006 people taking bupropion SR 150 mg twice a day for 12 weeks while they tried to quit smoking. Insomnia was the most common side effect on bupropion, reported by 12.2% versus 6.9% on placebo. It started a median of 6 days in, sooner than on placebo (17 days), and the first episode typically lasted about 2 to 3 weeks, about as long as insomnia on placebo. Nausea began around days 8 to 10 in every group and lasted about a week on bupropion. Most first episodes were rated mild.

Two caveats matter. Everyone in the trial was quitting smoking, with a target quit date on day 8, and nicotine withdrawal causes its own sleep trouble and anxiety. The trial also used the twice-daily SR form rather than once-daily XL, and it was funded by Pfizer and GlaxoSmithKline.

Weeks 2 to 4: The Dose Step Up

The label allows an increase to the usual target of 300 mg once daily after 4 days for depression, or after 7 days for seasonal depression. Because several side effects are dose-related, they can appear or intensify after this step.

Anxiety tends to arrive a little later than insomnia. In the EAGLES analysis, anxiety on bupropion (8.4% versus 6.0% on placebo) began a median of 12 days in, earlier than on placebo (23 days), and the first episode typically lasted 11 to 15 days, similar to placebo.

Here’s how the timing evidence lines up:

Side Effect	Typical Start	Typical Duration	Evidence
Insomnia	Median day 6	About 2 to 3 weeks	EAGLES, smokers on SR
Nausea	Days 8 to 10	About 1 week	EAGLES, smokers on SR
Anxiety	Median day 12	11 to 15 days	EAGLES, smokers on SR

All three estimates describe the first episode of each side effect in the EAGLES adverse event analysis, so treat them as a guide rather than a promise.

The label also calls for watching closely for worsening depression or suicidal thoughts in the first few months and after any dose change, and it flags anxiety, agitation, panic attacks, insomnia, and irritability as symptoms to report.

Months 2 and 3: What Fades and What Lingers

By this point, the early activating effects have often eased. In the EAGLES analysis, first episodes of the common side effects had median durations of 41 days or less, and the authors described them as transient and self-limited.

A few effects are better monitored over time:

• Weight: in Wellbutrin XL’s seasonal trials, which ran up to about 6 months, 23% lost 5 pounds or more versus 11% on placebo, while 11% gained that much versus 21% on placebo. Our guide to Wellbutrin and weight goes deeper.
• Blood pressure: in those same trials, high blood pressure was reported in 2% on bupropion versus none on placebo, and average systolic pressure rose 1.3 points versus 0.1. The label calls for checks before and during treatment.
• Dry mouth: it had the largest gap over placebo in those longer trials, 26% versus 15%. The NIH’s dental research institute warns that ongoing dry mouth raises the risk of tooth decay, and it suggests sipping water, chewing sugarless gum, limiting caffeine, and avoiding tobacco and alcohol.

Sexual side effects stay uncommon. In two 8-week bupropion XL trials of adults with normal sexual function at the start, orgasm problems at week 8 affected 15% on bupropion XL, 30% on escitalopram, and 9% on placebo, and the bupropion-placebo difference wasn’t statistically significant. A 2016 systematic review of 51 studies concluded that bupropion is generally well tolerated, has very low rates of sexual dysfunction, and is more likely to cause weight loss than gain.

Among people whose depression went into remission in a six-trial pooled analysis led by a GlaxoSmithKline researcher, fewer on bupropion than on SSRIs still had daytime sleepiness (19% versus 32%) or fatigue (20% versus 30%).

This is also when you and your prescriber can weigh side effects against benefit, since the Medication Guide notes it may take several weeks to feel Wellbutrin working.

Why Seizure Threshold Rules Shape the Timeline

Seizures are uncommon on Wellbutrin, but they explain why the schedule looks the way it does. The label reports seizures in about 0.1% of people (1 in 1,000) taking up to 300 mg a day of the SR form and about 0.4% at 300 to 450 mg of the immediate-release form. Risk rises almost tenfold between 450 and 600 mg a day, so the label says to increase the dose gradually, keep daily doses at or below 450 mg, and stop for good if a seizure happens.

Risk is also higher with a seizure disorder, a current or past eating disorder such as bulimia or anorexia, a severe head injury, or abruptly stopping alcohol, benzodiazepines, or seizure medicines, and these rule Wellbutrin out. It also shouldn’t be combined with any other bupropion product, and medicines that lower the seizure threshold, such as antipsychotics, some antidepressants, theophylline, and systemic steroids, call for extra caution.

Three everyday rules follow from this, all from the Medication Guide:

• If you miss a dose, skip it and take the next one at the usual time, because doubling up raises seizure risk.
• Swallow tablets whole, since chewing, cutting, or crushing releases the drug too fast.
• Limit or avoid alcohol, and if you drink heavily, don’t stop suddenly without talking to your prescriber.

Which Side Effects Need a Call Right Away?

Most side effects can wait for your next check-in, but these call for faster action:

• Seizure, trouble breathing, or swelling of the face, lips, or tongue: call 911.
• Thoughts of suicide or self-harm: call or text 988. Wellbutrin carries a boxed warning about suicidal thoughts in children, teens, and young adults.
• Rash, hives, itching, fever, swollen glands, or painful mouth sores: stop and call your prescriber, since these can signal a serious allergic reaction.
• Eye pain, vision changes, or swelling or redness around the eye: call promptly, as these can signal angle-closure glaucoma.
• Greatly increased energy, racing thoughts, reckless behavior, or seeing or hearing things that aren’t there: call your prescriber.
• New or worsening depression, anxiety, agitation, or irritability, especially after a dose change: call your prescriber.

How to Make Side Effects Easier to Live With

These practical steps come from the label and Medication Guide:

• Take Wellbutrin XL in the morning, as the label directs, and not too close to bedtime if sleep is a problem.
• Ask about pacing. In the seasonal trials, people who were unlikely to tolerate 300 mg could stay at or return to 150 mg.
• Tell anyone giving you a urine drug screen that you take bupropion, since it can cause false-positive amphetamine results.
• Don’t stop abruptly. The label advises stepping down from 300 mg to 150 mg before stopping, and our guide on how to taper off Wellbutrin covers the steps.

With Wellbutrin, the bumpiest stretch is often the first few weeks, which is exactly when a quarterly check-in leaves the biggest gap.

On Wellbutrin, activating effects like insomnia and anxiety tend to show up in the first two weeks and usually ease within a few weeks, a dose increase can bring them back, and weight and blood pressure are the ones to keep checking over months. If you’re weighing bupropion against an SSRI, our guide to Wellbutrin vs SSRIs walks through how prescribers choose.

Ready to take control of your mental health? Start your anonymous intake with Siggy and get your plan reviewed by a licensed prescriber.

This article is for education only and isn’t a substitute for personal medical advice. Don’t start, change, or stop a medication without talking to your prescriber. It was reviewed for clinical accuracy and reflects sources available as of September 2026.