*An off-label use of a medication is a use that is not FDA-approved. Prescribers can decide to use a medication off-label because, in their professional judgment, they believe it may offer a benefit to someone.
Prozac can feel different from person to person, but typically those on the medication see a benefit within the first two weeks of starting it. To see the full benefit, you should take Prozac for 4 to 8 weeks. It is also common to have side effects, especially within the first week of taking Prozac, but this should be mild, and most see them go away the longer they are on the medication.
If you want to discuss your current prescription with a provider or are considering a prescription for Prozac, an online psychiatry platform can be a good place to start. Platforms like Talkiatry and Brightside Health offer psychiatric assessments and prescription consultation, and can answer any questions you have about taking Prozac.
Boxed Warning: Fluoxetine (Prozac) - Risk of suicidal thoughts and behaviors in certain people
Fluoxetine, the active ingredient in Prozac, has a black box warning. These are the most serious types of warnings from the Food and Drug Administration (FDA). Fluoxetine can increase the risk of suicidal thoughts and behaviors in children, adolescents, and young adults. Regardless of your age, you should talk with your doctor about serious risks with fluoxetine and any other medications before starting treatment.
Online Psychiatry and Medication Management Covered by Insurance Talkiatry can match you with a real psychiatrist who takes your insurance and is seeing new patients. They’re in-network with major insurers and offer medication management. Get started with a short online assessment
What Is Prozac & How Does it Work?
Prozac, also known by its generic name fluoxetine, is a medication FDA-approved for its use in treating depression eating disorders like bulimia nervosa, and panic disorder with or without the fear of open spaces. Doctors may also prescribe Prozac for obsessive-compulsive disorder (OCD) It can be used in combination with Zyprexa (olanzapine) for treatment-resistant depression and depressive episodes associated with bipolar I disorder.
Prozac belongs to the drug class selective serotonin reuptake inhibitors (SSRI), where it works by blocking the neurons from reuptaking the chemical serotonin, leaving more for the body to work with. This is important because serotonin is linked to managing your mood and emotions.1, 2, 3
What Happens When You Start Taking Prozac?
While on Prozac, some people may experience changes immediately, while others may take a few weeks. The benefits you can see from Prozac should be in terms of what condition you are trying to treat. The negatives you would experience would be the side effects which might go away as you get more used to the medication.
Some beneficial effects people notice when they start taking Prozac include:1, 2, 3
- Improved mood/more manageable depression
- Lessened frequency of panic attacks
- Relief in OCD symptoms
- Improved appetite
- Improved energy
- Decreased binge eating episodes
What Side Effects Occur in the First Week with Prozac?
Short-term negative effects are a common occurrence during the first week of taking Prozac. Typically, Prozac’s side effects go away as the body adjusts to the medication, but some people experience these side effects for the entire duration of taking the medication. How you respond to the medication is largely dependent on individual factors, so you may or may not experience them. Side effects should be tolerable and should not impact your daily life. If you have concerns, then talk to a doctor or pharmacist.
Some negative effects people notice when they start taking Prozac include:1, 2, 3
- Unusual dreams
- Decreased desire or ability to have sex
- Flu-like symptoms (ie sweating, stuffy nose, etc)
- Nausea
- Loss of appetite
- Difficulty falling asleep or staying asleep
*All medications, Prozac, can cause side effects that can be mild or serious. This is not a comprehensive list of all possible side effects. You should talk with your doctor about any questions you have and to understand the potential side effects and benefits of any medication.
How Soon Will I Notice Prozac Working?
Prozac varies in the amount of time people need before they see benefits. A clinical research study4 found that over half of people on Prozac see a benefit within two weeks of starting the medication. They found that the probability of seeing a first-time benefit from Prozac within 4 and 6 weeks was 80.2% and 89.5%, respectively.
It was stated in the study that if there wasn’t a response within those 4 to 6 weeks, then there was about a 73 to 88% chance that there would be no response to Prozac at all by 8 weeks. This study measured responses with a biweekly Hamilton Depression Rating Scale, where they saw an improvement in depression symptoms in patients.
How Long Does it Take for Prozac to Work?
Usually, a person will see some benefits within the first week of taking the medication, but it will take 4 to 8 weeks to see the full effects of Prozac. During this time, the patient may experience changes in their sleeping and eating before their mood improves. If you are on Prozac, then you should take it as directed, even if it seems like it’s not working, so that you can give the medication a chance to work.5
How Do I Know If My Prozac Is Working?
Prozac, like other SSRIs, needs some time before you see the full benefits of being on it. No two people are alike, so you may see benefits immediately, while another person may take a few months to see the effects.
Typically, you may see full benefit around 4 to 8 weeks after starting Prozac, but sometimes a medication may not work for a person and they may need to consider other options.
Some ways to tell that Prozac may not be working for you include:6
- Decreased energy
- Changes appetite
- Loss of interest or pleasure in your usual activities
- Difficulty concentrating
- Worsening sleep
- Nervous energy
Online Psychiatry and Medication Management Covered by Insurance Talkiatry can match you with a real psychiatrist who takes your insurance and is seeing new patients. They’re in-network with major insurers and offer medication management. Get started with a short online assessment
When To Talk To Your Doctor
Like all medications, Prozac has side effects, but these side effects should be tolerable and sometimes they go away once the body gets used to it. If the side effects impact your daily life or you do not see a benefit after several weeks of use, then speak with a doctor. It is important not to stop taking the medication without medical supervision because it could lead to withdrawal symptoms. Take medications as prescribed unless your prescriber makes any changes to them.
Questions to Ask Your Doctor About How Prozac Makes You Feel
Before starting Prozac, you should be aware of what to expect. Questions you could ask involve how to take Prozac and what to be aware of so that the treatment is effective and safe. Be sure to ask a qualified healthcare professional, such as your doctor, psychiatrist, or therapist. Online psychiatry services are available to those who wish to change prescribers and want the convenience of a telehealth visit.
Questions to ask your care team about how long it may take Prozac to work:
- How long will it take for Prozac to work?
- What changes can I expect and what happens if I don’t notice any changes?
- What common side effects should I look out for?
- What happens if I miss a dose?
- How long will it take for me to adjust to taking Prozac?
- Am I at risk for more severe symptoms if I am already taking other anxiety/depression medications?
- What is the best dosage to ensure fewer side effects?
- Are there drugs I am taking that could have negative interactions?
- When should I reach out to you if I am experiencing side effects?
- Are there any serious side effects that I should be aware of?
- Will drinking alcohol affect the way this medication works?
- Is it safe to take Prozac and Adderall together?
In My Experience
In my experience, most people experience some benefits within a week of starting Prozac, but sometimes it does take around 4 to 8 weeks until you see the full benefits of the medication. Within the first week was typically when patients saw side effects, but they were usually tolerable and went away the longer they used the medication. Patients I have worked with have also seen a greater benefit from Prozac when they paired it with some form of therapy.
Follow the directions that your doctor gives you, and to not stop taking the medication by yourself. If you think that you are not seeing any benefit or are experiencing side effects, then you should speak with your doctor, psychiatrist, or pharmacist.
ChoosingTherapy.com strives to provide our readers with mental health content that is accurate and actionable. We have high standards for what can be cited within our articles. Acceptable sources include government agencies, universities and colleges, scholarly journals, industry and professional associations, and other high-integrity sources of mental health journalism. Learn more by reviewing our full editorial policy.
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Label: DailyMed. Prozac – fluoxetine hydrochloride. Retrieved from https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm
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Label: FDA. Prozac. Retrieved from https://www.accessdata.fda.gov/drugsatfda_docs/label/2021/018936s111lbl.pdf
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MedlinePlus. (Last Revised 2022, 15 January). Prozac. Retrieved from https://medlineplus.gov/druginfo/meds/a689006.html
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Nierenberg, A. A., Farabaugh, A. H., Alpert, J. E., Gordon, J., Worthington, J. J., Rosenbaum, J. F., & Fava, M. (2000). Timing of onset of antidepressant response with fluoxetine treatment. The American journal of psychiatry, 157(9), 1423–1428. Retrieved from https://ajp.psychiatryonline.org/doi/10.1176/appi.ajp.157.9.1423
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MedlinePlus. (n.d). Antidepressants. Retrieved from https://medlineplus.gov/antidepressants.html
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National Alliance on Mental Illness. (n.d) Fluoxetine (Prozac). Retrieved from https://nami.org/About-Mental-Illness/Treatments/Mental-Health-Medications/Types-of-Medication/Fluoxetine-(Prozac)
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