Fluoxetine Side Effects: What You’ll Actually Feel

Fluoxetine (brand name Prozac) is a popular SSRI used for depression, anxiety, and a few other conditions. It works by increasing serotonin levels in the brain, but that boost can bring a mix of pleasant and not‑so‑pleasant symptoms. Knowing what to expect helps you stay ahead of problems and decide if the drug is right for you.

Common side effects you’ll notice early on

Most people feel at least one of these within the first two weeks:

• Nausea or upset stomach – Happens to about 30% of users. Taking Fluoxetine with food often eases it.
• Headache – A dull or throbbing pain that usually fades after a few days.
• Dry mouth – Sip water, chew sugar‑free gum, or suck on a lozenge.
• Sleep changes – Some feel more awake, others get sleepy. Adjusting the time you take the pill (morning vs. evening) can help.
• Insomnia or vivid dreams – If dreams keep you up, talk to your doctor about a lower dose.

These symptoms are usually mild and disappear as your body gets used to the medication.

Less common but important side effects

While they’re rare, you should still be aware of them:

• Weight changes – Some people lose appetite and weight, others gain a few pounds.
• Sexual problems – Reduced libido, delayed orgasm, or erectile issues can affect up to 20% of users.
• Increased anxiety or agitation – Especially when you first start; it often settles down.
• Bleeding risk – Fluoxetine can thin blood a bit, so be careful with aspirin, NSAIDs, or warfarin.
• Serotonin syndrome – A serious but rare reaction that includes high fever, muscle stiffness, and confusion. It needs emergency care.

If any of these become severe or don’t improve, call your doctor.

Another red flag is the emergence of suicidal thoughts, especially in teens and young adults during the first month. Share any mood shifts with your prescriber right away.

Finally, remember that side effects can interact with other meds. Always list every prescription, over‑the‑counter drug, and supplement you take.

When you notice an issue, don’t just stop the pill. Talk to your doctor about lowering the dose, switching times, or trying a different SSRI. Most side effects can be managed without quitting the medication.

In short, Fluoxetine is effective for many, but it isn’t a one‑size‑fits‑all. Knowing the typical side‑effect profile, recognizing warning signs, and staying in touch with your healthcare provider will give you the best chance of a smooth experience.