How Long Does Prozac Stay In The System? Timeline And Variables

Last Updated: January 26, 2021

Authored by Roger Weiss, MD

Reviewed by Michael Espelin APRN

Prozac (Fluoxetine) is a drug used in the treatment of depression. It is also prescribed for the treatment of other psychological disorders such as anxiety disorders. To those who have wondered if Prozac is a narcotic, it is not. However, being a drug that acts on the brain and causes some adverse effects, it is not uncommon to wonder how long does Prozac stay in the system?

After ingesting Prozac, its active ingredient called “Fluoxetine” is absorbed in the gut and undergoes a first-pass metabolism in the liver where it is metabolized via demethylation reactions into its norfluoxetine metabolites. Fluoxetine undergoes a demethylation reaction catalyzed by hepatic enzymes converting  R- and S-fluoxetine to R- and S–norFluoxetine enantiomers respectively. After leaving the liver, Fluoxetine with its norFluoxetine metabolites is circulated in the bloodstream to the tissues.

Prozac Half-life Timeline

sand watch on a beachFluoxetine has a half-life of 2 to 7 days; however, norfluoxetine lasts longer with a half-life of 4 to 15 days. Knowing this timeline, how long does Fluoxetine last in the body? Fluoxetine stays in the system for about 2 to 3 months after the last dose, when nor-Fluoxetine is completely excreted. This prolonged half-life of norFluoxetine is responsible for the long duration of some of the Fluoxetine adverse effects such as depressed mood and sexual side effects.
When an individual quits Prozac abruptly, the body will react in certain ways. These reactions are called the withdrawal symptoms. These symptoms usually begin within 2 to 4 weeks of quitting the drug and lasts for about 2 weeks. Some of these withdrawal symptoms include anxiety, mood swings, rebound depression, fatigue, dizziness, headache, muscle cramps, insomnia, and tremors. In case of Fluoxetine overdose, withdrawal symptoms can be more severe and impede elimination of the drug from the body.

Factors that Determine How long Prozac Stays in The Body

Generally, how long Prozac stays within the system varies a lot depending on several factors. While some individuals may completely excrete the drug as early as 21 days, it may take close to 3 months to completely excrete it in other individuals. Factors which influence the duration of the drug within the body include:

1. Individual Differences

Individual factors which determine the length of stay of Fluoxetine within the body include age and sex, body weight, liver function, genetic profile, and metabolic rate. Elderly individuals usually have a longer Fluoxetine half-life than young adults. Also, the larger an individual’s body weight, the longer the half-life of Prozac as a result of the large surface area for tissue deposition of the drug. Liver impairment, food intake with drugs, and genetic variants causing underexpression of the liver enzymes are associated with long Prozac half-life.

2. Duration of Use

Patients who have been taking Fluoxetine for a prolonged duration are likely to have the drug accumulate more in the tissues, and the longer the duration of use, the longer the tissue deposition of the drug. Furthermore, the longer the duration of use, the more likely an individual is to develop the long-term effects of Prozac such as anxiety and sleep disturbances.

3. Drug Interactionsassortment of different medications

Co-administration with other drugs may affect the rate of metabolism of Prozac. Drugs that affect the function of the cytochrome P450 enzymes will, in turn, affect the rate of metabolism of the drug.

How Long Prozac Stays in The Blood, Hair, and Urine?

After ingesting a dose, it remains in the urine for up to 96 days. In the blood, however, it stays for a much shorter period because of its short Prozac timeline which results from the first-pass metabolism in the liver. Also, it lasts in the hair for a few weeks, however, drug hair tests are unlikely to detect Fluoxetine.

How to Get Prozac out of The System

Here are some tips to help eliminate the drug from the body faster:

1. Stop the Usage

Until an individual discontinues Fluoxetine, it keeps accumulating in the tissues and bloodstream, and the more it accumulates, the higher its half-life and its stay in the system.

2.Burn Caloriesmah jogging in the park

Fluoxetine binds strongly to fatty tissues, making it accumulate for as long as one takes the drug. Regular exercise, therefore, burns fats which leads to a shorter Prozac half-life and faster release into the bloodstream for clearance by the kidneys. A weight loss on Fluoxetine will be a nice bonus. Other methods of eliminating it faster include the use of activated charcoal and drugs which induce CYP2D6.
Prozac is one of the most commonly prescribed antidepressants and its rate of metabolism and clearance from the body varies between individuals. However, It may take a between 2 weeks to 3 months before it is completely eliminated from the body.
If someone is taking Prozac and needs information about how it affects the body, please call our 24-hour-helpline (888)-459-5511 to speak to one of our treatment support advisors who will answer the questions confidentially.

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Published on: June 27th, 2018

Updated on: January 26th, 2021

About Author

Roger Weiss, MD

Dr. Roger Weiss is a practicing mental health specialist at the hospital. Dr. Weiss combines his clinical practice and medical writing career since 2009. Apart from these activities, Dr. Weiss also delivers lectures for youth, former addicts, and everyone interested in topics such as substance abuse and treatment.

Medically Reviewed by

Michael Espelin APRN

8 years of nursing experience in wide variety of behavioral and addition settings that include adult inpatient and outpatient mental health services with substance use disorders, and geriatric long-term care and hospice care.  He has a particular interest in psychopharmacology, nutritional psychiatry, and alternative treatment options involving particular vitamins, dietary supplements, and administering auricular acupuncture.


Leave a comment

  • Nosheen Hood
    I was taking fluxetine 20 mg for almost a year on my doctor prescription. Now I’ve stopped taking it for about 2 weeks. I want to know does it show in my regular blood or urine test as I’m going to have a medical examination for my immigration to Canada? And also I want to know the side effects of quitting the medicine abruptly. Thanks
    • OMG-read
      Did you actually READ the article?
  • Stefanie
    I was taking 10mg of Prozac for approximately one month, because of some side effects the doctor took me off of it. How long will it take to leave my system if I have only been taking it for a month?
    • Sally
      I have the same situation, but only took it for 10 days. Hopefully it will leave soon!
    • Rick
      Do you remember how long it took in your situation? Rick
  • Ian kilpatrick
    I’ve been on fluoxetine for six weeks and had to stop taking it because of the bad head Ake and stumec akes I stop taking it Friday how long will the withdrawal symptoms last I’ve got head Ake and stumec akes still