Can Increasing Your Dose Of Prozac Cause Anxiety?

In our latest question and answer, the pharmacist discusses whether or not increasing your dose of Prozac can cause anxiety symptoms and how long you can expect them to last if they do occur.

Can Increasing Your Dose Of Prozac Cause Anxiety?
Jun 15, 2020

Robin asked

I was increased in Prozac from 20 mg to 30 mg a week ago and I have felt more anxiety as a result. My doctor says it’s breakthrough symptoms, not the Prozac. How long do breakthrough symptoms last?

At a glance

  • SSRI’s like Prozac are not fast acting medications. They can take anywhere from 4-12 weeks for you to see benefits. This is typically the case if you are just starting the medication or increasing the dose. About 15% of patients so experience anxiety when starting a SSRI that usually resolves.
  • If the breakthrough symptoms are due to life circumstances, the medication might take a bit before it helps.


Hi Robin and thank you for your question. I’m glad that you turned to your physician to help manage your mental health. Occasionally, it’s necessary to change the dose of a medication, even if that same dose seemed to help better in the past.

Fluoxetine (or under the brand Prozac) was the first selective serotonin reuptake inhibitor approved for use over 30 years ago, so we have decades of research and outcomes that we can look to.

When it comes to fluoxetine, most side effects tend to occur when the medication is started for the first time. Generally, these side effects gradually resolve and you’ll start to experience the positive antidepressant effects of the medication after being on the medication for 4-12 weeks.

Typically, if you increase the dose of the medication, you may experience similar side effects as when you first started the medication. These are usually milder since you have probably been on the medication for a while at this point.

Research suggests that about 15% of patients starting or changing their SSRI dose do experience a worsening amount of anxiety that generally improves after 4-12 weeks of therapy. When you first started taking fluoxetine, did you experience anxiety? If so, you’ll probably see this anxiety resolve over the course of the next few weeks. If you didn’t, then it is probably related to life circumstances and not the medication.

When it comes to SSRI’s, the best advice that I can give any patient starting or changing their dose is patience! If your breakthrough anxiety that you are experiencing is due to life circumstances, the fluoxetine will help, but it might take another month or two. In that time, I hope that your life situation improves. Good luck, and just remember that the medication is effective, it just takes a while to help.

  • Fluoxetine monograph, Pubchem
  • 2. What are the clinical implications of new onset or worsening anxiety during the first two weeks of SSRI treatment for depression?, Depression and Anxiety

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