How long does it take for Prozac (fluoxetine) to work?

Prozac (fluoxetine) is an antidepressant that’s regularly used to treat depression, OCD, and a variety of anxiety disorders. If you’ve been prescribed Prozac, you’re probably wondering how long it will take to start working, and when exactly you can expect to feel better. Like many medications, how long it takes to work depends on a few different factors, including why you’re taking it. In general though, you should start to notice small changes over the course of the first several weeks.

In this article, we’ll cover how long it takes Prozac to work for different mental health conditions, what it feels like when it starts working, and what to look out for.

How long does Prozac take to work?

Prozac is the brand name for the SSRI (selective serotonin reuptake inhibitor) fluoxetine. The amount of time it takes to work varies on the medical condition you’re taking it for and your symptoms, but typically it takes a few weeks to feel the full benefits.  

• Major depressive disorder (MDD): It can take between 4 to 8 weeks to feel the full effect of the medication. But people in some clinical trials have reported a lessening of their symptoms of depression after just 2 weeks.  
• Obsessive-compulsive disorder (OCD): It can take 4 to 6 weeks for Prozac to work, though it may take up to 12 weeks for some people. OCD symptoms also tend to respond to higher doses of SSRIs than lower doses, so this can add to the time.
• Bulimia nervosa: Some studies have shown that people notice relief from their symptoms within 3 weeks of taking the medication.  

Your doctor will likely start you on a low dose of Prozac, adjusting it over time to reach the right dose for you. Remember, never increase your dose without talking to your doctor first.  

What does Prozac feel like when it starts working?

Research indicates that if the dose of Prozac that you’re taking is effective for your symptoms, you may notice signs that it’s working within the first week or two. But if you haven’t noticed any differences after taking Prozac for 4-6 weeks, you most likely won’t respond to the medication at this dose, or Prozac might not be right for you.

Here are eight common signs that Prozac is working:  

• You find yourself enjoying life more fully.
• You feel less depressed or anxious
• You have more energy.
• You’re sleeping better.
• You have a more regular appetite.
• You have an easier time doing your normal daily activities.
• You’re less preoccupied by your mental health symptoms.
• You have a reduced desire to binge eat or throw up (if you’re taking it for an eating disorder like bulimia).

Side effects of Prozac

Another way you might know medication is working is that you’ll start to feel some of its common side effects. For Prozac, these include nausea, drowsiness, dry mouth, and sexual side effects, including sexual dysfunction.  

When is the best time of day to take Prozac?

Many people find it beneficial to take Prozac in the morning because it can interfere with your sleep. However, some patients find Prozac to be sedating. Talk to your psychiatrist about sleep interruptions from Prozac in order so they can help determine the best course of action to take next.  

No matter when you decide to take it, try to take it at the same time each day. This can help you feel Prozac’s effects more consistently.  

What should you look out for when taking Prozac?

During the first three weeks of taking Prozac, you may  notice some mild common side effects—like trouble sleeping, agitation, headache, stomach upset, or decreased sexual drive—though these usually will go away within a week or two.

If you experience a lot of discomfort—including increased suicidal thoughts—or find the effects don’t get better over time, talk to your doctor. They may decide to decrease your dose or have you try another medication.  

When you begin taking any new medication, it’s important to keep an eye on your symptoms and how you’re feeling. Consider keeping a journal to take notes, and share it with your doctor. This way they can help make sure the medication is working the way it’s supposed to.

And if Prozac does help you feel better, don’t stop taking it on your own. Stopping medication suddenly can have negative effects or “withdrawal symptoms,” so let your doctor know first if you want to stop and they can help come up with a plan for you to go off Prozac safely and effectively.  

FAQs

Here's what else to know about Prozac's timing and effects.

How does Prozac work?

Prozac works by increasing the levels of serotonin, a neurotransmitter in the brain that helps regulate mood, in order to alleviate symptoms of depression, anxiety, and other related conditions.

Does Prozac work immediately?

The effects of Prozac may not be immediately noticeable, and it typically takes several weeks for the medication to reach its full therapeutic effect. How long pindividuals may start experiencing positive changes in their symptoms within the first few weeks of treatment.

What are other treatment options for anxiety?

Alternatives to Prozac include other SSRIs like Zoloft (sertraline) and Paxil (paroxetine), SNRIs like Effexor (venlafaxine), MAOIs (monoamine oxidase inhibitors), TCAs (tricyclic antidepressants), and atypical antidepressants.

The information in this article is for education and informational purposes only and should never be substituted for medical advice, diagnoses, or treatment. If you or someone you know may be in danger, call 911 or the National Suicide and Crisis Lifeline at 988 right away.