Key Takeaways

• Cymbalta (duloxetine) can cause sleepiness or drowsiness, especially when first starting the medication or when increasing the dose.
• Sleepiness is one of the common side effects, but some people experience the opposite, trouble sleeping.
• Factors like dosage, other medications, supplements, and your overall health condition can affect how tired you feel.
• Severe or persistent drowsiness should be discussed with a healthcare professional for safety and possible dose adjustments.

What Is Cymbalta?

Cymbalta, the brand name for duloxetine, is an antidepressant classified as a serotonin and norepinephrine reuptake inhibitor (SNRI). It is FDA-approved for several conditions, including:

• Major depressive disorder (MDD)
• Generalized anxiety disorder (GAD)
• Fibromyalgia
• Diabetic neuropathy
• Chronic pain and musculoskeletal pain

Cymbalta comes in delayed-release capsules, meaning the medication is released slowly to improve tolerability and absorption. Like many antidepressants, it affects chemicals in the brain that regulate mood, stress response, and pain.

Does Cymbalta Make You Sleepy?

Drowsiness and sleepiness are listed among the common side effects of Cymbalta, especially during the first few weeks of taking Cymbalta. Many patients notice tiredness as their body adjusts to the medication’s effects on serotonin and norepinephrine.

However, it’s important to note that while some people experience drowsiness, others report insomnia or trouble sleeping.

Why Cymbalta Causes Drowsiness

There are several reasons Cymbalta may cause you to feel tired:

Changes in neurotransmitters

As an SNRI, duloxetine affects the levels of serotonin and norepinephrine. Early changes in these neurotransmitters can slow reaction times and cause fatigue.

Disrupted sleep quality

For some, the medication may interfere with falling asleep or staying asleep, leading to poor quality nighttime rest and subsequent daytime fatigue.

Interactions with other medications or supplements

Combining Cymbalta with certain medications can cause an increased risk of fatigue or lead to serious side effects.:

• St. John’s wort
• Ibuprofen
• Monoamine oxidase inhibitors (MAOIs) like phenelzine
• Wellbutrin (bupropion)
• Over-the-counter sleep aids
• Antidepressants like Lexapro or other SSRIs

Always get medical advice before mixing medications.

Underlying health conditions

People with chronic pain, mental health conditions, or high blood pressure may feel more tired when starting new therapy.

Withdrawal symptoms

Stopping duloxetine abruptly may cause fatigue, dizziness, and headaches. Always follow your doctor’s tapering instructions to avoid withdrawal symptoms.

How Long Does the Sleepiness Last?

For many individuals, Cymbalta-related drowsiness improves as their body adjusts, usually within the first few weeks. If sleepiness lasts beyond this time, contact a healthcare provider to reassess your dose, timing, or possible interactions.

Who Is More Likely to Feel Sleepy on Cymbalta?

You might experience increased drowsiness if you:

• Are new to SNRIs or have switched from an SSRI
• Take other medications that cause sedation
• Have liver problems or metabolic issues
• Combine duloxetine with alcohol, cannabis, or sedating supplements
• Take higher doses or increase the dosage too quickly

Your PharmD, nurse, or doctor can help evaluate these risk factors.

Other Side Effects to Watch For

While drowsiness is possible, Cymbalta can cause other side effects, including:

Common side effects

• Nausea
• Headache
• Dizziness
• Diarrhea
• Increased sweating
• Dry mouth
• Constipation
• Loss of appetite or weight changes (including weight loss or weight gain)
• Stomach pain
• Trouble sleeping
• Sexual side effects such as a decreased sex drive, erectile dysfunction, and difficulty achieving an orgasm

More serious side effects (seek medical attention)

• Suicidal thoughts, especially in young adults
• Signs of serotonin syndrome (agitation, fever, confusion)
• Serious skin reactions
• Severe dizziness
• Low sodium (confusion, weakness)
• Eye pain or worsening glaucoma
• Serious, life-threatening allergic reaction
• Severe liver problems (yellowing of skin, dark urine)

Does Cymbalta Make You Sleepy at Certain Times of Day?

You may notice feeling sleepy at specific times, depending on when you take Cymbalta:

• Morning sleepiness, if taken too early
• Afternoon fatigue during the adjustment period
• Evening tiredness if taken later in the day

If Cymbalta makes you too tired, your provider may recommend switching the timing of your next dose to reduce daytime drowsiness.

How to Reduce Sleepiness While Taking Cymbalta

Adjust dosing time

Ask your provider whether taking Cymbalta in the evening may help reduce daytime tiredness.

Avoid supplements or OTC products that cause sedation

Check all medications and supplements for interactions—especially sleep aids, antihistamines, and herbal products.

Stay hydrated and nourish your body

Since Cymbalta may cause loss of appetite, maintaining a healthy diet and drinking plenty of water can help with fatigue.

Monitor mental health and mood changes

Watch for signs of worsening depression, daytime sleepiness, or other mental health changes.

Listen to your doctor

Never adjust your dose or stop taking Cymbalta without speaking to your provider.

When to Call a Healthcare Professional

Seek medical help immediately if you notice:

• Sudden or worsening sleepiness
• Difficulty waking up
• Severe eye pain or worsening glaucoma symptoms
• Suicidal thoughts or mental status changes
• Signs of serotonin syndrome
• Skin reactions or hives

Takeaway

Yes, Cymbalta can make you sleepy, especially when you first start taking it or during dosage increases. While many people notice fatigue or sedation, others experience trouble sleeping. These are both normal responses to an SNRI adjusting brain chemistry.

If sleepiness becomes disruptive, a healthcare professional can help adjust timing, dosage, or evaluate other causes of your fatigue. With proper monitoring and guidance, Cymbalta remains a safe and effective treatment for mood disorders, anxiety, chronic pain, and fibromyalgia.

Sources

• Lupin Pharmaceuticals, Inc. Duloxetine capsule, delayed release [package insert]. Last updated 11/2025. DailyMed. Accessed Dec. 1, 2025.