How Long Does It Take For Prozac To Work?

Kristin Hall

Reviewed by Kristin Hall, FNP

Written by Our Editorial Team

Published 05/16/2021

Updated 05/17/2021

For the 18.6 percent of women who take an antidepressant each day, these drugs can be lifesavers, working to decrease levels of depression and anxiety so patients can feel emotionally stable and be able to follow a normal daily routine. 

They also relieve symptoms of restlessness, and can help reduce sleep problems and prevent suicidal thoughts.

Prozac®, also known as fluoxetine, is an antidepressant that helps manage conditions such as major depressive disorder (MDD), obsessive compulsive disorder (OCD), panic disorder, bulimia nervosa and premenstrual dysphoric disorder (PMDD)

Part of a class of medications called selective serotonin reuptake inhibitors (SSRIs), it does this by helping the brain maintain healthy levels of serotonin, which regulates mood. 

Those taking Prozac might feel more relaxed and less anxious. They may sleep better and have increased levels of energy and be better able to focus on tasks.

If you’re considering starting Prozac, you’re probably eager to know how long it will take to work, and how you can expect to feel once it does. 

The answer will largely depend on the individual, but most sources note that it can take anywhere from two to four weeks.

Learn how Prozac works for anxiety here.

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Healthcare providers will typically start a patient on a low-dose of medicine while he or she monitors potential side effects. 

These can include nausea, trouble sleeping and headaches. They typically go away after a few weeks. 

Other side effects can include dry mouth, diarrhea, feeling restless or nervous and increased sweating. 

Sexual side effects such as problems with orgasm or ejaculation may not go away over time.

If you’re taking a daily dose, you may start at 20mg and may go up to 80mg. Those on a once-a-week regimen may take a 90mg dose. 

Within a week, you may to see improvement in sleep, and have more energy and appetite, which can be a sign that the Prozac is working. 

It could take up to six to eight weeks to see your mood and desire to participate in activities improve.

In addition to the potential side effects, there are other issues that patients may experience when on a Prozac regimen.

Taking Prozac while in the last few months of pregnancy can cause problems in newborns following delivery. 

Discuss with your healthcare provider if you plan to become pregnant or do become pregnant while on Prozac. Our blog answers Is It Safe To Take Prozac® While Pregnant? in more detail.   

You’ll also want to tell your healthcare provider if you have had a heart attack or heart failure, or have diabetes, seizures or liver or heart disease. 

Patients who have low levels of potassium or magnesium in the blood or have ever undergone electroshock therapy should disclose this to their healthcare provider as well.

Prozac can cause drowsiness, and drinking alcohol can exacerbate this. It can also contribute to angle-closure glaucoma. 

This is a condition in which fluid is unable to flow out of the eye causing a quick, severe increase in eye pressure which may lead to a loss of vision. 

If you have eye pain or changes in vision while taking Prozac talk to your healthcare provider immediately.

In rare cases, children, teens and young adults who took Prozac experienced an increase in suicidal thoughts. It is unclear how widespread this side effect is as it was measured in clinical studies. 

Speak to a healthcare provider about this risk and if taking Prozac for its mood-boosting effects outweighs it.

Don’t skip doses when taking Prozac. If you do, take the missed dose as soon as you remember  — unless it’s almost time for your next dose. 

In that case, skip the missed dose and stick to your regular dosing schedule.

Once you begin to feel better, you may be tempted to stop taking Prozac. Doing so can result in withdrawal symptoms like irritability, nausea, dizziness, vomiting, nightmares, headache or paresthesias, which is a prickling, tingling sensation on the skin — so don’t do it. 

Keep all appointments with your healthcare provider and discuss with them what might be a good time, if any, to wean yourself off your medication.

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Prozac is one of the most popularly prescribed antidepressants on the market — and for good reason. It works.

However, one of the most popular questions people ask before taking it for the first time is: how long will it take for it to start helping?

The answer is tricky and varies person to person, but generally, you should start feeling results within two to four weeks.

However, like all other prescription medications, Prozac comes with some potential side effects, from mild to wild, including everything from nausea and sleep disruption, to certain sexual issues and withdrawal if stopped abruptly.

8 Sources

Hims & Hers has strict sourcing guidelines to ensure our content is accurate and current. We rely on peer-reviewed studies, academic research institutions, and medical associations. We strive to use primary sources and refrain from using tertiary references.

  1. Brody, MPH, Debra J., and Qiuping Gu, MD, PHD. “Antidepressant Use Among Adults: United States, 2015-2018.” Centers for Disease Control and Prevention, September 2020,
  2. [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. Depression: How effective are antidepressants? [Updated 2020 Jun 18]. Available from:
  3. “Fluoxetine (Prozac).” National Alliance on Mental Illness,
  4. Chu A, Wadhwa R. Selective Serotonin Reuptake Inhibitors. [Updated 2020 Nov 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from:
  5. Judge, R., et al. “Changes in energy during treatment of depression: an analysis of fluoxetine in double-blind, placebo-controlled trials.” PubMed, 20 December 2000,
  6. Sohel AJ, Shutter MC, Molla M. Fluoxetine. [Updated 2020 Jun 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from:
  7. The Food and Drug Administration. (n.d.). PROZAC (fluoxetine hydrochloride) Pulvules for oral use.
  8. “Fluoxetine.” US National Library of Medicine,

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.

Kristin Hall, FNP

Kristin Hall is a board-certified Family Nurse Practitioner with decades of experience in clinical practice and leadership. 

She has an extensive background in Family Medicine as both a front-line healthcare provider and clinical leader through her work as a primary care provider, retail health clinician and as Principal Investigator with the NIH

Certified through the American Nurses Credentialing Center, she brings her expertise in Family Medicine into your home by helping people improve their health and actively participate in their own healthcare. 

Kristin is a St. Louis native and earned her master’s degree in Nursing from St. Louis University, and is also a member of the American Academy of Nurse Practitioners. You can find Kristin on LinkedIn for more information.

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