Effexor Side Effects: What's Common and How Long It Lasts
The most common Effexor XR side effects are nausea, insomnia, dizziness, sleepiness and sweating.
By withClaro Editorial · 2026-11-02 · 4 min read
Clinical section reviewed by Dr. Jason Tan , Consultant Psychiatrist, on October 27, 2026.
Key takeaways In the FDA trials, nausea was the most common Effexor XR side effect: 30% against 12% on placebo. Insomnia, dizziness, sleepiness, dry mouth and sweating were all more common than on placebo. In 100 r/Effexor threads, sexual side effects, sweating and tiredness were the side effects people named most. Effexor can raise blood pressure, so the label asks for it to be checked before and during treatment. On this page
What are the most common side effects of Effexor? Which side effects people on r/Effexor named How long do Effexor side effects last? Which Effexor side effects are serious? What should you tell your prescriber about Effexor side effects? The most common Effexor XR (venlafaxine) side effects are nausea, insomnia, dizziness, sleepiness, dry mouth and sweating. In the FDA trials across all its uses, nausea affected 30% of people against 12% on placebo. Nausea and dizziness often ease as the body adjusts, but on r/Effexor most people who said how long their side effects lasted were still having them when they posted.
What are the most common side effects of Effexor?
The label pools 3,558 people on Effexor XR and 2,197 on placebo across trials in depression, generalized anxiety, social anxiety and panic disorder, at doses from 37.5 to 225 mg, so it is an average across four conditions and the whole dose range. The side effects seen most often, compared with placebo, were:
Side effect Effexor XR Placebo Nausea 30% 12% Insomnia 18% 10% Dizziness 16% 10% Sleepiness 15% 8% Dry mouth 15% 5% Weakness 13% 8% Sweating, including night sweats 11% 3% Loss of appetite 10% 3% Constipation 9% 3%
Sexual side effects affect women and men. Lower sex drive affected 5.1% against 1.6% on placebo; being unable to reach orgasm affected 3.6% of men against 0.1%, and 2.0% of women against 0.2%; men also had problems with ejaculation or orgasm, 9.9% against 0.5%. Trial figures like these are probably low, because people rarely raise sex unless asked.
Which side effects people on r/Effexor named
Sexual side effects, sweating and tiredness were what people on r/Effexor named most. These are people's own accounts, not trial measurements, and people with ongoing problems are more likely to post, so treat them as a range of experiences rather than odds. We read 100 recent threads about side effects on r/Effexor, comments included, and 216 people described their own experience; 13 of them said they had noticed nothing. One person could name several:
What they named Of 216 people Lower libido or orgasm problems 48 Sweating 38 Tiredness or drowsiness 35 Nausea or stomach trouble 34 Emotional flatness 24 Trouble sleeping 20
One person on r/Effexor wrote:
I still sweat profusely in my sleep
Another had a quieter time:
I don't think I've encountered one side effect.
How long do Effexor side effects last?
On r/Effexor, of 51 people who said how long theirs lasted, 30 said they were still going, 16 that they eased within weeks and 5 that they lasted months and then eased; many threads are written early, before things have had time to settle. It also depends on the side effect: early ones such as nausea and dizziness tend to ease as the body adjusts, while sweating and sexual side effects are the ones people often describe as lasting.
Which Effexor side effects are serious? Medically reviewed by Dr. Jason Tan on October 27, 2026, this section only.
First, the label's boxed warning: antidepressants raised suicidal thoughts and behavior in people under 24 in trials, and the risk is highest in the first months and after a dose increase.
The label also warns that Effexor can raise blood pressure in a dose-related way. It asks for blood pressure to be measured before starting and regularly during treatment, and for high blood pressure to be brought under control first. Other warnings include serotonin syndrome, bleeding, and angle-closure glaucoma, where MedlinePlus says eye pain, changes in vision such as colored rings around lights, and swelling around the eye need a doctor straight away. Stopping suddenly can bring withdrawal symptoms, which the label covers separately; more in Effexor withdrawal . The clinical view:
Most early side effects of antidepressants ease within the first weeks, while a few tend to last and are worth raising.
Call your prescriber the same day, or get urgent care, if you notice:
- new or worse thoughts of suicide or self-harm, especially early on, after a dose change, or in people under 25 - agitation, heavy sweating, fever, muscle twitching or confusion, which can be signs of serotonin syndrome - unusual bleeding or bruising, black or tarry stools, or vomiting blood - a sudden burst of energy, little need for sleep, racing thoughts or unusual risk-taking, especially if you or a close relative has bipolar disorder If you're having thoughts of harming yourself, contact emergency services or a crisis line straight away. In the US, call or text 988. In the UK, call Samaritans on 116 123. Elsewhere, find a crisis line near you .
What should you tell your prescriber about Effexor side effects?
Tell your prescriber which side effects you have, when they started and whether they are easing, so you can decide together whether to wait or change the plan. It helps to tell them:
When you started Effexor, your dose and any recent change. Which side effects you have and how strong they are. Whether they're easing, steady or getting worse. Your blood pressure readings, if you check them. Other medications you take, including migraine and pain medicines. Download on the App Store Side effects on Effexor rise and fade over weeks, and a daily record shows which ones are easing. The withClaro app lets you log mood, sleep, energy and side effects each day, linked to your dose, and turns it into a report for your prescriber.
Frequently asked questions Why does Effexor make you sweat? The label lists sweating, including night sweats, as a common side effect. Tell your prescriber if it's hard to live with.
Does Effexor raise blood pressure? It can, and the risk rises with the dose. The label asks for blood pressure to be measured before starting and regularly during treatment.
What happens if I miss a dose of Effexor? MedlinePlus says to take it when you remember, skip it if the next dose is nearly due, and never take a double dose. Venlafaxine leaves the body quickly, and many people describe feeling unwell after a missed dose, so tell your prescriber if it happens.
When is a side effect a reason to change the dose? Bring it to your prescriber when it is still strong after the first weeks, gets worse, or gets in the way of sleep, work or relationships. Any change to the dose is decided with them, not alone.
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Sources EFFEXOR XR (venlafaxine) prescribing information, US Food and Drug Administration via DailyMed, revised August 2023 MedlinePlus: Venlafaxine Claro articles are for self-monitoring and educational purposes only. They are not a medical device, therapist, or diagnostic tool, and do not replace care from your prescribing clinician. If you are in crisis, contact your care team, emergency services, the Samaritans (UK: 116 123), or the Crisis Text Line (US: text HOME to 741741).