Starting an Antidepressant: What to Expect in the First Six Weeks

The first weeks on an antidepressant are when most people have questions, and when many stop taking it. The reason is simple: side effects tend to show up in the first few days, while the benefit takes weeks. Knowing the usual timeline makes it much easier to get through that gap.

This guide covers the most commonly prescribed antidepressants, SSRIs and SNRIs. Other medications follow somewhat different patterns, so ask your prescriber what applies to yours.

Days 1 to 14: Side Effects Come First

Early side effects are common and usually mild. Most fade within one to two weeks as your body adjusts.

• Stomach upset: nausea or loose stools. Taking the medication with food helps.

• Headache: usually mild and short-lived.

• Feeling jittery or more anxious: this can be unsettling when anxiety is the reason you started. It usually passes, and starting at a low dose reduces it.

• Sleep changes: some people feel drowsy and others feel wired. Moving the dose to morning or evening often solves this.

None of these mean the medication is wrong for you. If they are hard to tolerate, call your prescriber before stopping. A slower start often fixes the problem.

Weeks 2 to 4: Early Signs

Improvement usually arrives in pieces. Sleep, energy, and appetite often shift before mood does. Family members may notice you seem a little lighter before you feel it yourself. Some improvement by the two-week to four-week mark is a good sign that the medication will help.

Weeks 4 to 8: The Fuller Effect

Mood, interest, and anxiety typically improve over four to six weeks at an adequate dose, and gains can continue for a few weeks after that. If there has been little or no change by then, the usual next steps are raising the dose, switching medications, or adding something. Needing an adjustment is common. In large studies, only about one in three people reach full remission on the first antidepressant they try, and most people who keep working with their prescriber find something that helps.

When to Call Right Away

• New or worsening thoughts of suicide or self-harm. This is uncommon, and the risk is highest in people under 25 during the first weeks and after dose changes. Call your prescriber right away, or call or text 988 at any time.

• Unusual agitation or restlessness that feels very different from your normal self.

• Signs of mania: sleeping very little without feeling tired, racing thoughts, unusually high energy, or uncharacteristic risk-taking.

• High fever, stiff or twitching muscles, and confusion, especially if you take other medications that affect serotonin.

• A rash, swelling, or trouble breathing, which can signal an allergic reaction and needs urgent care.

Side Effects That Can Linger

Sexual side effects, weight change, sweating, and feeling emotionally flat do not always fade with time. They are common reasons people stop treatment without telling anyone. Please raise them. There are usually good options, including adjusting the dose, changing the timing, or switching to a medication less likely to cause the problem.

Practical Tips

• Take it every day. Antidepressants do not work when taken only as needed.

• If you miss a dose, take it when you remember unless it is nearly time for the next one. Do not double up.

• Go easy on alcohol, which can worsen mood and sleep and add to drowsiness.

• Do not stop suddenly. Stopping abruptly can cause dizziness, irritability, and flu-like symptoms. When it is time to come off, taper with your prescriber.

• Keep your follow-up visit. The first check-in, usually within two to four weeks, is where dose and side effects get sorted out.

Common Questions

How long will I need to take it? For a first episode of depression, the usual recommendation is to continue for at least six to twelve months after you feel well, since stopping earlier raises the chance of relapse.

Will it change my personality? No. When an antidepressant is working, most people say they feel more like themselves. If you feel numb or flat, tell your prescriber.

Are antidepressants addictive? They do not cause cravings or a high. They can cause discontinuation symptoms if stopped abruptly, which is why a gradual taper matters.

Worth a Conversation

If you are starting a medication, or have tried one and are not sure it is working, a careful follow-up makes a real difference. At SANA Psychiatry, we provide psychiatric evaluation and medication management for adults in Missouri, Illinois, and Florida, in person and by video. You can schedule an appointment online.

Written by Sindhura Saini, board-certified psychiatrist (American Board of Psychiatry and Neurology). Last reviewed October 2026. This article is for education and is not a substitute for an individual medical evaluation.