Mirtazapine: what it treats, how to take it, side effects
Last updated September 3, 2026.
Mirtazapine is an antidepressant in its own class - and the one doctors reach for when depression comes with insomnia and a lost appetite. You may know it as Remeron. It increases certain types of activity in the brain to maintain mental balance, and its side effect profile is its personality: sedating, appetite-boosting, bedtime-only.
What does it treat?
Depression is the labeled use. The sedation and weight gain that count as side effects for some patients are exactly why it gets chosen for others - people who cannot sleep and cannot eat.
How do you take it?
Once a day at bedtime, with or without food. The label starts at 15 mg in the evening and increases, if needed, no more often than every 1 to 2 weeks, up to 45 mg a day. It also comes as a disintegrating tablet: open the blister with dry hands, place it on your tongue, let it dissolve, and swallow with saliva - no water needed, use it right out of the pack, and never split it. Full benefit takes several weeks or longer. Do not stop suddenly; your doctor will decrease the dose gradually. Missed dose: take it when you remember unless the next one is close; never double up.
Side effects to know
- Common: drowsiness, dizziness, and increased weight and appetite.
- Serious: flu-like symptoms, fever, chills, sore throat, mouth sores, or other signs of infection (a rare blood-cell drop - call the doctor immediately); the serotonin-syndrome cluster of fever, sweating, confusion, fast or irregular heartbeat, severe muscle stiffness or twitching, agitation, hallucinations, loss of coordination, nausea, vomiting, or diarrhea; chest pain or fast heartbeat; headache with unsteadiness and thinking or memory problems; unusual bleeding or bruising; allergic reactions with facial or throat swelling; and seizures. Angle-closure glaucoma: eye pain, nausea, colored rings around lights, and eye swelling or redness mean emergency care. The boxed warning covers increased suicidal thoughts and actions in people under 24.
Who should not take it?
Anyone who has taken an MAO inhibitor, linezolid, or methylene blue within the past two weeks. Flag long QT syndrome in you or your family, a past heart attack, low blood pressure, high cholesterol or triglycerides, and heart, kidney, or liver disease. The disintegrating tablets contain aspartame, which matters for PKU. It will make you drowsy - that is partly the point - but no driving until you know how it affects you. Alcohol worsens its side effects. Pregnancy and breastfeeding need a direct call with your doctor.
When is it an emergency?
Call 911 for seizures, trouble breathing or swallowing, or facial or throat swelling. Fever with sore throat or mouth sores, and the serotonin-syndrome cluster, mean immediate care. Thoughts of harming or killing yourself mean calling your doctor right away - or call or text 988, the Suicide and Crisis Lifeline, any time. For an overdose, call Poison Control at 1-800-222-1222. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Why is mirtazapine taken at bedtime?
Because sedation is its strongest immediate effect, so the label puts the dose in the evening before sleep. For people whose depression comes with insomnia, that side effect is the feature - it restores sleep while the antidepressant effect builds over the following weeks. Taking it in the morning would mean fighting drowsiness all day.
Will mirtazapine make me gain weight?
Increased weight and appetite are on MedlinePlus's common side effect list - it is one of the more weight-prone antidepressants. For people whose depression suppressed appetite, that is often welcome and even why it was chosen. If the gain becomes a problem, it is a dose-and-alternatives conversation with your doctor, not a reason to quit suddenly.
Why did my doctor pick mirtazapine instead of an SSRI?
Usually the insomnia-plus-poor-appetite picture, or a bad experience with SSRIs. Mirtazapine works through a different mechanism than SSRIs - it increases certain types of brain activity rather than blocking serotonin reuptake - so it also gets used when an SSRI did not work or its side effects (especially sexual ones) were a problem.
Can I drink alcohol while taking mirtazapine?
MedlinePlus says to talk to your doctor about the safe use of alcohol, because alcohol can make mirtazapine's side effects worse. With a medication this sedating, alcohol stacks the drowsiness and coordination problems heavily - skipping it is the standard advice.
How do I take the dissolving mirtazapine tablet?
With dry hands, open the blister pack and place the tablet on your tongue. It disintegrates there and you swallow it with saliva - no water needed, per MedlinePlus. Use it immediately once removed from the pack, and do not split the disintegrating tablets.
How long does mirtazapine take to work?
Sleep and appetite often improve in the first days to weeks; the full antidepressant benefit takes several weeks or longer, per MedlinePlus. The label changes doses no more often than every 1 to 2 weeks, since each level needs time to show what it does.