Does Prozac cause daytime sleepiness? (3+ tips)

In this article, we will answer the question, “Does Prozac cause daytime sleepiness?”. We will discuss what research has to say in this regard, factors influencing the occurrence of daytime sleepiness while on Prozac and how to manage daytime sleepiness effectively.

Does Prozac cause daytime sleepiness?

Prozac may cause daytime sleepiness in some individuals taking the medication. This side effect is not very common and tends to occur at the start of therapy, if at all. Daytime sleepiness with Prozac normally subsides once the body adjusts to the medication.

Prozac (also known as Fluoxetine) is an antidepressant belonging to the class of SSRIs (selective serotonin reuptake inhibitors) and approved by the FDA for monotherapy or as an adjunct in various depressive illnesses and bulimia nervosa (1).

Prozac is known to be an activating antidepressant (that does not cause sedation), but sometimes it may cause excessive daytime sleepiness. This can be due to the fatigue and sedation caused by Prozac which can lead to the individual feeling drowsy or sleepy. The mechanism behind this effect can be the effect of Fluoxetine on other neurotransmitters like histamine and acetylcholine.

How does Prozac impact the sleep-wake cycle?

Although Prozac is considered to be the least sleep architecture disrupting from all the SSRIs, it can impact the sleep-wake cycle. Prozac tends to increase wake time by decreasing the amount of rapid eye movement (REM) sleep. It also increases REM latency and causes slow wave sleep (SWS) (2).

These mechanisms can cause increased wake window, difficulty falling and staying asleep and insomnia in some individuals. This is mostly reported at the initiation of therapy and with doses between 20-40mg/day of Fluoxetine. This side effect tends to go away after a few weeks of treatment with Fluoxetine (2).

If Prozac induces changes in the sleep architecture of any individual taking the medication, the effects can be long-lasting due to the longer half-life of the medication (2).

What does research suggest?

Research and case studies on excessive daytime sleepiness caused by Fluoxetine are scarce. As this is not a very common side effect, only a few research studies have been published.

A case study assessed the symptoms of a 21-year-old female taking Fluoxetine for anxiety for the past 10 months. She reported excessive daytime sleepiness for almost 6 months. She described that she has the desire to sleep 5 or 6 times in the day. Discontinuation of Fluoxetine resolved her symptoms and brought down her excessive sleep habits (3).

Another research study reported the occurrence of insomnia as a side effect of Fluoxetine use. Staying awake at night due to insomnia may cause excessive daytime sleepiness in individuals. The study further stated that this side effect can be overcome by alternative antidepressants if the body does not adapt within a few weeks (4).

A clinical study examining the effects of Fluoxetine and dothiepin in normal volunteers also noted the occurrence of daytime sedation in individuals taking the medication. Sleep disturbances were found to be worse in the early weeks of treatment (5).

Another study examining the effect of Fluoxetine on the sleep-wake cycle reported that Fluoxetine did not cause daytime sleepiness in individuals undergoing treatment however, it did make the individuals more drowsy. This effect was attributed to the insomnia caused by Fluoxetine (6).

What factors influence daytime sleepiness while on Prozac?

Various factors can lead to daytime sleepiness while on Prozac:

Individual variations

Each individual is different and the response of individuals to Prozac may also vary from person to person. Individual variations in response to Prozac can cause daytime sleepiness as a side effect.

Prozac-induced insomnia

A very common side effect reported with Prozac use is the occurrence of insomnia. Insomnia can lead to daytime fatigue and sedation.

Drug interactions

If the individual is taking other medications like sedating agents, they can interact with Prozac. There can also be an increased risk of the occurrence of daytime sleepiness when using Prozac with such medications.


Elderly individuals tend to experience sleep disturbances more often than younger adults. Age can affect the body’s response to various medications and cause unwanted side effects. Prozac-induced daytime sleepiness can be exacerbated due to this reason.

Timing of dose

The time of taking Prozac depends on the individual. Sometimes taking Prozac at night may interfere with your sleep pattern, causing insomnia. That is why, to avoid sleep problems your healthcare provider may recommend taking this medication in the morning.

Underlying medical conditions

Sleep disorders or any other underlying medical condition that can alter sleep may be a cause of excessive daytime sleepiness in individuals while on Prozac.

Lifestyle factors

An unhealthy lifestyle, inadequate sleep, improper nutrition and excessive use of stimulants like coffee, can contribute to the occurrence of excessive daytime sleepiness in individuals undergoing treatment with Prozac.

How to manage daytime sleepiness while taking Prozac?

If you feel that Prozac is the cause of your excessive daytime sleepiness and it has become very discomforting then there are a few things that you can do to help with your condition. Some tips for minimizing and coping with daytime sleepiness while taking Prozac are as follows:

Change the timing of the medication

Some individuals benefit more by taking Prozac during the daytime. The excessive sleepiness experienced during the day and the insomnia at night can also be minimised.

Regulate sleep patterns

Improving sleep patterns and habits can help your body get an adequate amount of sleep. This can also lower the chances of daytime sleepiness and fatigue.

Limit caffeine and alcohol

Both caffeine and alcohol can interact with Prozac to increase side effects. Caffeine is a stimulant used to keep the mind alert. Excessive consumption of caffeine can disrupt sleep patterns and cause daytime sleepiness. Alcohol causes sedation and can worsen the symptoms of sleepiness and drowsiness, whether day or night.

Lifestyle improvements

Healthy and nutritious food and a proper routine of exercise can help improve sleep quality and patterns in individuals. They can also help with overall energy levels and help you feel more energised.

Alternative treatments

If Prozac continues to cause daytime sleepiness and your symptoms do not subside, or get worse, you can request your healthcare provider for an alternative treatment for your condition. Your doctor will assess your situation and recommend the best treatment according to your needs.

Consult your healthcare provider

Seeking professional advice and communicating your concerns to your doctor regarding your condition or the side effects that you are experiencing is a crucial part of therapy. Keeping your healthcare provider informed of any side effects can save you from any serious and potentially life-threatening side effects.

To the best of my knowledge and according to research, Prozac may rarely cause daytime sleepiness. Very few cases have been reported of such a side effect linked to Prozac use. If such a side effect does occur, it mostly self-resolves within the first few weeks of treatment. You can also use some techniques to help minimise such a side effect.

In my opinion, if you do experience daytime sleepiness due to Prozac use, it is best to inform your healthcare provider. Your doctor will assess your situation and adjust your treatment plan to minimise side effects and manage your symptoms.

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The Food and Drug Administration (FDA). HIGHLIGHTS OF PRESCRIBING INFORMATION. PROZAC® (fluoxetine capsules) for oral use. Available from: 


Leba LK, Demir AB. Fluoxetine-Associated Sleep Disorders-Report of Two Cases and Literature Review. Journal of Turkish Sleep Medicine. 2021 Sep 1;3:170-3.


Fava M. Daytime sleepiness and insomnia as correlates of depression. J Clin Psychiatry. 2004 Jan 1;65(Suppl 16):27-32.


Wilson SJ, Bailey JE, Alford C, Weinstein A, Nutt DJ. Effects of 5 weeks of administration of fluoxetine and dothiepin in normal volunteers on sleep, daytime sedation, psychomotor performance and mood. Journal of psychopharmacology. 2002 Jul;16(4):321-31.


Nicholson AN, Pascoe PA. Studies on the modulation of the sleep-wakefulness continuum in man by fluoxetine, a 5-HT uptake inhibitor. Neuropharmacology. 1988 Jun 1;27(6):597-602.

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