The first week on Lexapro is an adjustment period, and for most people it feels worse before it feels better. Your body is reacting to rising serotonin levels before your brain has had time to adapt, which means you may experience a mix of physical side effects and even a temporary increase in anxiety. The therapeutic benefits typically don’t kick in for two to four weeks, so that first week can feel discouraging. Here’s what to actually expect.
The Most Common Physical Side Effects
Nausea is the side effect people notice first, often within hours of taking the initial dose. It can range from mild queasiness to a feeling that you can’t eat a full meal. Headaches are also very common in the first few days. Both of these tend to improve within the first week or two as your body adjusts to the medication.
Other common side effects during this window include dry mouth, increased sweating, fatigue or feeling weak, trouble sleeping, and, somewhat contradictorily, feeling drowsy during the day. Not everyone gets all of these. Some people sail through the first week with just mild nausea, while others feel like they have a low-grade flu. The intensity varies a lot from person to person, but these effects occur in more than 1 in 100 people who take the drug.
Why Anxiety Can Get Worse Before It Gets Better
This is the part that catches people off guard. Lexapro works by increasing serotonin availability in your brain, but during the first days of treatment, serotonin levels fluctuate before they stabilize. Those fluctuations can temporarily amplify the very anxiety you’re trying to treat. About 7% of people starting an antidepressant develop what’s sometimes called “jitteriness syndrome,” a distinct pattern of increased nervousness, restlessness, and agitation in the early weeks.
This doesn’t mean the medication isn’t working or that it’s the wrong one for you. It means your brain chemistry is in transition. You might feel more on edge than usual, have racing thoughts, or notice a jittery, keyed-up sensation that’s hard to pin down. For most people, this fades as serotonin levels even out over the following weeks.
What It Feels Like Emotionally
Don’t expect to feel “better” during week one. The mood-lifting effects of Lexapro take time to build, so what you’ll mostly notice in the first seven days is the absence of improvement combined with new physical discomfort. That combination can feel demoralizing, especially if you worked up the courage to start the medication and were hoping for quick relief.
Some people describe feeling emotionally flat or slightly disconnected. Others feel more irritable than usual. Sleep disruption, whether it’s difficulty falling asleep or waking up earlier than normal, can amplify all of these feelings. It’s a rough patch with a clear end point: most of these early emotional shifts settle down within the first two weeks.
Reducing Side Effects in the First Week
A few practical adjustments can make the first week more manageable. Taking Lexapro with food is one of the simplest ways to blunt nausea. Eating smaller, more frequent meals throughout the day also helps. If nausea is persistent, sucking on sugarless hard candy, sipping cool water, or trying an over-the-counter antacid can take the edge off.
Timing matters too. If the medication makes you drowsy, taking it in the evening may help. If it disrupts your sleep, a morning dose might work better. Many prescribers start patients at a lower dose and increase it after a week or two specifically to minimize these early side effects, so if your starting dose feels like too much, that’s worth a conversation with whoever prescribed it.
Symptoms That Need Immediate Attention
Most first-week side effects are uncomfortable but harmless. A smaller set of symptoms requires a call to your prescriber right away. These include new or significantly worsening depression, panic attacks that weren’t there before, feeling unusually agitated or aggressive, acting impulsively, or having thoughts of self-harm. The FDA specifically flags the early weeks of antidepressant treatment as a period when unusual behavioral or mood changes should be reported immediately.
This doesn’t mean Lexapro is dangerous for most people. It means the adjustment period deserves attention. If you live with someone or have a close friend you see regularly, it’s worth letting them know you’ve started a new medication so they can flag changes you might not notice yourself.
When You’ll Start Feeling the Benefits
The timeline that frustrates most people is this: side effects show up in days, but the actual antidepressant and anti-anxiety benefits take two to four weeks to become noticeable, sometimes longer. The first week is almost entirely about your body adapting to the drug, not about reaping its rewards. By week two, the most bothersome physical side effects like headaches and nausea are usually fading. By week four, you’re in a much better position to evaluate whether the medication is actually helping.
The key thing to remember about week one is that it’s not representative of what Lexapro will feel like long term. It’s the adjustment cost, not the final product. Almost everything that feels wrong during those first seven days is temporary.