Doxepin Side Effects: What to Expect and When to Call Your Doctor

Like all medications, doxepin comes with potential side effects that vary depending on the dose you're taking. The side effect profile looks very different at the low doses (3–6 mg) used for insomnia versus the higher doses (25–150 mg) used for depression and anxiety. Understanding what to expect — and what to watch for — helps you use doxepin safely.

FDA Boxed Warning: Suicidal Thoughts and Behaviors

Doxepin carries the FDA's most serious warning (a black box warning) about increased risk of suicidal thoughts and behaviors in children, adolescents, and young adults up to age 24, particularly during the first few months of treatment or after dose changes. This warning applies to all antidepressants, not just doxepin.

If you or someone you know is experiencing suicidal thoughts, call or text 988 (Suicide & Crisis Lifeline) or call 911. Seek emergency care immediately.

Common Side Effects of Doxepin

These side effects occur most often and are typically manageable:

• Drowsiness and sedation: The most common side effect, especially in the first few weeks. This is intentional at the low doses used for insomnia, but can be problematic at antidepressant doses. Avoid driving or operating heavy machinery until you know how doxepin affects you.
• Dry mouth (xerostomia): Caused by doxepin's anticholinergic properties. Staying hydrated, using sugar-free gum, and maintaining good dental hygiene can help.
• Constipation: Another anticholinergic effect. Adequate fluid intake and fiber-rich diet can help. Discuss with your doctor if this becomes significant.
• Nausea: More common when starting doxepin or increasing the dose. Taking with food may help, although for Silenor (insomnia tablets), this medication should not be taken within 3 hours of a meal.
• Blurred vision: Anticholinergic effect on the eye's ciliary muscle. Usually mild. Tell your doctor if this persists.
• Weight gain: Doxepin, like many antidepressants, can cause weight gain with long-term use — especially at higher antidepressant doses. This is less of a concern at the 3–6 mg doses used for insomnia.
• Dizziness: May occur especially when standing up quickly (orthostatic hypotension). Rise slowly from sitting or lying positions.

Serious Side Effects: Call Your Doctor or Seek Emergency Care

These side effects are less common but require prompt medical attention:

• Serotonin syndrome: Occurs when doxepin is combined with other serotonergic medications (SSRIs, SNRIs, MAOIs, St. John's Wort). Symptoms include rapid heart rate, high fever, sweating, shaking, muscle stiffness, and confusion. Seek emergency care immediately.
• QT prolongation: Doxepin can affect heart rhythm at higher doses. Symptoms include fast, irregular heartbeat, dizziness, or fainting. Tell your doctor immediately if you experience these.
• Mania or hypomania: Patients with undiagnosed bipolar disorder may experience a manic episode when taking doxepin or any antidepressant. Signs include elevated mood, decreased need for sleep, rapid speech, and impulsive behavior.
• Urinary retention: Difficulty urinating is a known anticholinergic effect. Call your doctor if you have trouble emptying your bladder fully.
• Angle-closure glaucoma: Doxepin's anticholinergic effects can trigger acute angle-closure glaucoma in susceptible individuals. Symptoms include sudden eye pain, blurred vision, seeing halos, and headache. This is a medical emergency.
• Sleep-related behaviors (Silenor): Doxepin tablets for insomnia may rarely cause sleep-related behaviors such as sleep-driving, sleep-walking, sleep-eating, or sleep-talking. Tell your doctor immediately if this occurs.

Are Side Effects Worse at Higher Doses?

Yes. Side effects are generally much milder at the 3–6 mg doses used for insomnia compared to 75–150 mg doses used for depression. At very low doses, doxepin acts primarily as an antihistamine with minimal anticholinergic effects. At higher antidepressant doses, the full spectrum of TCA side effects emerges. This is why doxepin is considered well-tolerated for insomnia but carries more risks at antidepressant doses.

What to Expect When You First Start Doxepin

Most patients notice sedation within the first few days. Other side effects like dry mouth and constipation are common in the early weeks and may improve over time as your body adjusts. For antidepressant effects, you typically won't feel the full benefit for 2–4 weeks or longer. Don't stop taking doxepin because of early side effects without talking to your doctor first.

For a full list of medications and substances that interact with doxepin and can worsen side effects, see our guide: Doxepin Drug Interactions: What to Avoid and What to Tell Your Doctor.