Does Fluoxetine Make You Tired? Sleepiness, Insomnia and What Helps (UK)

Does fluoxetine make you tired? What the NHS and leaflet say

Yes. Fluoxetine (sometimes sold as Prozac) is an SSRI antidepressant used for depression, OCD and bulimia, and sometimes for menopause symptoms. The NHS lists “feeling dizzy or drowsy (sleepy)” and “problems sleeping” among its common side effects. The UK leaflet goes further and puts fatigue and insomnia in its very common group.

The leaflet also lists poor concentration and dizziness as common, which can feel like tiredness too. If you feel dizzy or drowsy, the NHS says don’t drive, ride a bike or use machinery until it has gone. For yawning on its own, see why am I yawning so much?

Does fluoxetine make you sleepy or keep you awake?

It can do either. Insomnia is one of the most frequent side effects in the leaflet, so many people find fluoxetine keeps them awake or gives them broken nights and vivid dreams, then feel tired the next day. Others feel drowsy or sleepy in the day. Both are listed, and both often settle as your body gets used to it.

The leaflet says feelings of weakness, drowsiness or confusion happen mostly in older people and in people taking diuretics (water tablets), and to tell your doctor straight away if you get them. Alcohol makes drowsiness worse: the NHS says it’s best not to drink while taking fluoxetine. See alcohol and sleep, vivid dreams and insomnia.

Why fluoxetine can make you tired

• Broken sleep. Insomnia and unusual dreams are common, and a poor night shows up as a tired day. See how to stay asleep.
• Direct drowsiness. Fatigue, tiredness and sleepiness are listed side effects in their own right.
• The condition itself. The NHS lists lack of energy and disturbed sleep among the symptoms of depression, so tiredness may be from low mood rather than the tablet. See low mood.
• Something else. Other medicines such as beta blockers, statins or weight-loss injections (Mounjaro and Wegovy), or low iron, low B12 or an underactive thyroid. For the bigger picture, see why am I always tired?

How long does fluoxetine tiredness last?

Often a couple of weeks. The NHS says some side effects ease after a couple of weeks as your body gets used to fluoxetine, but some can last longer. The leaflet says most side effects are likely to disappear with continued treatment. If tiredness still bothers you after that, or affects daily life, speak to a pharmacist or your doctor.

Fluoxetine itself takes a few weeks to work. The NHS says your doctor may start you on a lower dose and increase it after 3 or 4 weeks, so you may notice side effects again for a short time after a dose change. The leaflet says your doctor should see you a couple of weeks after you start.

What is the best time to take fluoxetine?

The NHS doesn’t name a best time of day. It says take fluoxetine once a day at the same time each day, with or without food. If it keeps you awake at night or makes you drowsy in the day, ask your pharmacist or prescriber whether a different time of day would suit you better, rather than changing it on your own.

If you miss a dose, the NHS says take it as soon as you remember, unless it’s nearly time for the next one. Never take 2 doses to make up for a missed one.

What helps tiredness on fluoxetine

1. Talk to a pharmacist or your doctor. The NHS says they may be able to suggest ways to reduce side effects. If you’ve just started, you can ask a pharmacist about the New Medicine Service.
2. Keep taking it unless you’re advised to stop (see below).
3. Skip alcohol. It adds to drowsiness.
4. Keep regular sleep times. The NHS insomnia advice is to wake and get up at the same time every day, avoid caffeine for about 6 hours before bed and not to nap in the day. See sleep hygiene and sleep debt.
5. Don’t drive when drowsy. Wait until you know how fluoxetine affects you.
6. Ask about blood tests if tiredness lasts: iron, B12 and thyroid are common checks. See iron deficiency and vitamin B12 deficiency.

Should I stop fluoxetine if it makes me tired?

No, not on your own. The NHS says don’t suddenly stop fluoxetine because it may cause withdrawal symptoms: speak to your doctor first, who will lower the dose gradually over several weeks or months. The leaflet lists sleep disturbances and unusual tiredness or weakness among the withdrawal effects, so stopping suddenly can make tiredness worse, not better.

Your doctor can look at the dose, the timing or a different medicine if side effects don’t settle.

When to get urgent help

The leaflet says thoughts of self-harm can be more likely when you first start an antidepressant, and to contact your doctor or go to a hospital straight away if you have them. You can report side effects through the MHRA Yellow Card scheme.

Supplements and CBD with fluoxetine: check first

No supplement treats fluoxetine side effects. The NHS asks you to tell your doctor about any herbal remedies, vitamins or supplements, and says not to use St John’s wort with fluoxetine. The leaflet adds tryptophan to the list that raises the risk of serotonin syndrome, so check before taking tryptophan or 5-HTP.

CBD: CBD can interact with some medicines, there’s little direct research with antidepressants such as fluoxetine, and drowsiness can add up. The FSA advises people taking any medication not to take CBD unless under medical direction, so we don’t suggest CBD alongside fluoxetine. Speak to your prescriber or pharmacist first, and see can CBD interact with medication?

Our pick

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Our Reishi Mushroom Adaptogenic Complex isn’t suggested here: its pack says it isn’t for people on medication. For more on magnesium and sleepiness, see does magnesium make you sleepy?

iIf you take any regular medicines, check with your GP or pharmacist first. We don’t recommend our products during pregnancy or breastfeeding. For adults (18+) only.