Yes, fatigue is a recognized side effect of Lexapro (escitalopram). In clinical trials for major depressive disorder, 5% of people taking Lexapro reported fatigue compared to 2% on placebo. Sleepiness (somnolence) was even more common, affecting 6% of participants. The rates are higher when Lexapro is used for generalized anxiety disorder: 8% reported fatigue and 13% reported sleepiness.
How Common Fatigue Is by Condition
The likelihood of experiencing fatigue on Lexapro partly depends on what you’re taking it for. In trials for generalized anxiety disorder, fatigue and sleepiness were roughly twice as common as in depression trials. That 13% somnolence rate for anxiety (versus 7% on placebo) makes drowsiness one of the more frequent side effects in that group.
These numbers also mean that most people taking Lexapro don’t experience significant fatigue. But if you do, you’re far from alone, and the pattern is consistent enough that the FDA lists both fatigue and somnolence as treatment-emergent adverse events.
Why Lexapro Causes Fatigue
This is where things get a little puzzling, even for researchers. Many older antidepressants cause drowsiness because they block histamine receptors (the same ones that drowsy allergy medications target) or muscarinic and adrenergic receptors. Lexapro has virtually no affinity for any of these receptors. Its primary action is blocking the reuptake of serotonin, keeping more of it available in the brain.
The exact reason increased serotonin activity leads to fatigue in some people isn’t fully understood. Serotonin plays a role in regulating sleep-wake cycles, and flooding the system with more of it, especially before the brain adjusts, likely disrupts that balance. The fact that fatigue tends to fade over time supports the idea that it’s related to the brain’s initial adjustment period rather than a permanent effect of the drug.
When Fatigue Starts and How Long It Lasts
Fatigue typically shows up within the first week of starting Lexapro. For most people, it fades after one to two weeks as the body adjusts to the medication. If your fatigue persists beyond that window, it’s worth bringing up with your prescriber, because it may signal a need for a dose adjustment or a different approach.
Fatigue From Lexapro vs. Fatigue From Depression
This distinction matters because the very conditions Lexapro treats, depression and anxiety, are themselves major causes of fatigue. If you’ve been exhausted for weeks or months before starting the medication, it can be hard to tell whether your tiredness is the drug or the illness. A few clues help separate them.
Medication-related fatigue usually has a clear starting point: it appears or worsens within days of beginning Lexapro or increasing the dose. Depression-related fatigue, by contrast, tends to be persistent and present before treatment. If your energy was already low and doesn’t change after starting Lexapro, the medication probably isn’t the culprit. If you notice a distinct new wave of tiredness shortly after your first dose, the drug is the more likely explanation.
As Lexapro takes its full therapeutic effect (usually four to six weeks), many people find that their overall energy improves because the underlying depression or anxiety lifts. So early fatigue from the medication can give way to better energy in the longer run.
How to Manage It
The simplest adjustment is switching when you take your dose. If Lexapro makes you drowsy during the day, taking it at bedtime can turn that side effect into a minor benefit. This is a common recommendation, though it’s worth confirming the timing change with your prescriber first.
Beyond timing, a few practical strategies can help you get through the adjustment period:
- Short daytime naps. A 20-to-30-minute nap can offset the worst of the drowsiness without disrupting nighttime sleep.
- Light physical activity. Even a short walk can counteract the sluggishness. Exercise increases alertness through mechanisms that work independently of serotonin.
- Avoiding risky tasks. Hold off on driving or operating heavy machinery during the first couple of weeks if drowsiness is significant.
- Dose adjustment. If fatigue doesn’t resolve after two weeks, a lower dose may provide the therapeutic benefit with less sedation.
How Lexapro Compares to Other SSRIs
Sleepiness is not unique to Lexapro. Zoloft (sertraline), the other most commonly prescribed SSRI, lists sleepiness as a common side effect as well. Because all SSRIs work by increasing serotonin availability, fatigue and drowsiness are a shared class effect rather than something specific to Lexapro. That said, individual responses vary considerably. Some people feel more tired on one SSRI than another, so switching medications is a reasonable option if fatigue remains a problem after the adjustment period.