Week 3 on an Antidepressant: When the Body Settles

Week three is, in most clinical descriptions, the week when the body begins to settle on an antidepressant. NICE, RANZCP, and Royal College of Psychiatrists patient resources consistently describe the third week as when most early physical side effects ease meaningfully for the majority of patients — even though the mood benefit has typically not yet arrived.

What tends to ease in week three

Nausea is usually gone. Headaches have typically softened. Sleep often improves, though vivid dreams may persist. The jittery or wired feeling, if it appeared, generally fades. Dizziness has usually settled. By the end of week three, most patients report a return to baseline physical sensation, with the medication present but no longer dominating the experience.

What does not change yet

Mood is typically unchanged or only subtly different at week three. The mood benefit takes four to six weeks for most patients; week three is too early to assess therapeutic effect. This is a moment where some patients conclude the medication is not working — but absence of mood change at week three is not evidence; it is the expected pattern.

What to do in week three

Continue the dose consistently. No dose changes unless your prescriber directs them — week three is not an assessment point for therapeutic effect.

Continue your daily record. Patterns become more visible across three weeks than across one. Note what has eased and what has not.

Notice what has eased. Physical side effects returning to baseline is a meaningful signal — it means the medication is being tolerated as expected.

Look to week four to six as the next milestone. That is when the first mood changes typically appear for most patients on a suitable medication and dose.

What to flag to your prescriber

Raise these at your follow-up appointment or sooner

Side effects have not eased at all between week one and week three.
New side effects appearing in week three rather than easing.
New or worsening suicidal thoughts.
Any concern that the medication is producing unexpected effects.

Frequently asked questions

Should mood be improving by week three?

Usually not. Mood typically begins to shift in weeks four to six. Week three is when the body settles, not when mood improves. Absence of mood change at week three does not mean the medication is not working.

What if I still feel terrible in week three?

Discuss with your prescriber. Persistent side effects past week three are worth addressing — dose adjustment or other options may help. Don't stop or adjust the medication without guidance.

Is week three when I'll know if the medication is working?

No — week six to eight is the typical decision point for therapeutic effect. Week three is too early for that assessment. It is, however, a reasonable point to assess physical tolerability.

Evidence and sources referenced

NICE Guideline NG222 — Depression in adults: treatment and management (United Kingdom).
Royal Australian and New Zealand College of Psychiatrists (RANZCP) — Clinical Practice Guidelines for Mood Disorders.
NPS MedicineWise — prescriber and patient resources on antidepressant treatment (Australia).
Royal College of Psychiatrists — patient information on antidepressants.
TGA and FDA — product information for SSRI and SNRI medication classes.
Maudsley Prescribing Guidelines in Psychiatry — prescribing patterns and side-effect timelines.