Cymbalta Side Effects: What's Common and How Long It Lasts
The most common Cymbalta side effects are nausea, dry mouth, sleepiness and sweating, and many ease in the first weeks.
By withClaro Editorial · 2026-11-02 · 4 min read
Clinical section reviewed by Dr. Jason Tan , Consultant Psychiatrist, on October 27, 2026.
Key takeaways In the FDA trials for depression and anxiety, the most common Cymbalta side effects were nausea, dry mouth, sleepiness, constipation and sweating. In 100 r/cymbalta threads, nausea or stomach trouble, tiredness, sweating and insomnia were the side effects people named most. Of those who said how long side effects lasted, more said they were still going than said they had eased. Call your prescriber about yellowing skin or eyes, dark urine, new thoughts of self-harm or signs of serotonin syndrome. On this page
What are the most common side effects of Cymbalta? What 259 people on r/cymbalta said about side effects How long do Cymbalta side effects last? What should you tell your prescriber about Cymbalta side effects? The most common Cymbalta (duloxetine) side effects are nausea, dry mouth, sleepiness, constipation and sweating. In the FDA trials for depression and generalized anxiety, nausea affected 23% of people against 8% on placebo, and dry mouth 14% against 6%. Nausea and sleepiness often ease in the first weeks, while sweating and sexual side effects are more likely to stay, and a few side effects need a call the same day.
What are the most common side effects of Cymbalta?
Nausea, dry mouth, sleepiness, constipation and sweating, with nausea furthest ahead: 23% against 8% on placebo. These figures come from the label's pooled trials in depression and generalized anxiety, with 4,797 people on Cymbalta and 3,303 on placebo; the label reports its pain trials separately.
Side effect Cymbalta Placebo Nausea 23% 8% Dry mouth 14% 6% Sleepiness 9% 3% Constipation 9% 4% Tiredness 9% 5% Dizziness 9% 5% Insomnia 9% 5% Sweating 6% 2% Decreased appetite 6% 2%
Headache was as common on placebo, at 14%. Erectile dysfunction affected 4% against 1%, and lower libido 3% against 1%.
What 259 people on r/cymbalta said about side effects
We read 100 recent threads about side effects on r/cymbalta, comments included, and 317 people described their own experience. These are people's own accounts, not trial rates, and people with ongoing problems are more likely to post, so treat this as a range of experiences rather than odds. Of the 317, 259 named at least one side effect; nausea or stomach trouble came up most, then tiredness, sweating and trouble sleeping. One person can be in several rows:
What they named Of 259 people Nausea or stomach trouble 70 Tiredness or drowsiness 66 Sweating 60 Trouble sleeping 57 Anxiety or agitation 36 Lower libido or orgasm problems 31
How long do Cymbalta side effects last? Medically reviewed by Dr. Jason Tan on October 27, 2026, this section only.
Of 88 people on r/cymbalta who said how long their side effects lasted, more were still going when they posted (47) than had eased within weeks (36), and 5 said they lasted months. For some, the worst passed within days; one person wrote:
but after the fourth day, i started sleeping! idk if the full no-anxiety effects have started, but the worst of the side effects seem to have passed!
Side effects and benefit run on different clocks. Duloxetine acts from the first doses and reaches steady levels in the blood in about 3 days, which is why side effects come early; the benefit, which depends on the brain adjusting, can take 1 to 4 weeks or longer, MedlinePlus says. Of 68 people on r/cymbalta who said what helped, waiting it out, changing the time of the dose and a dose change came up most; dose changes were made with a prescriber. The clinical view on which side effects pass and when to call:
Side effects that often pass include nausea, an upset stomach, headache, sleep changes and feeling restless. If sexual side effects, weight change or feeling emotionally flat appear, they tend to stay while you take the medication. A change of dose or medication often helps with these, so mention them instead of putting up with them.
Call your prescriber the same day, or get urgent care, if you notice:
- new or worse thoughts of suicide or self-harm, especially early on, after a dose change, or in people under 25 - agitation, heavy sweating, fever, muscle twitching or confusion, which can be signs of serotonin syndrome - unusual bleeding or bruising, black or tarry stools, or vomiting blood - a sudden burst of energy, little need for sleep, racing thoughts or unusual risk-taking, especially if you or a close relative has bipolar disorder ## Which Cymbalta side effects are serious?
The most serious warning is in a box at the top of the label: suicidal thoughts and behavior can rise in children, teenagers and young adults aged 24 and younger, most of all in the first months and after a dose change. If you're having thoughts of harming yourself, contact emergency services or a crisis line straight away. In the US, call or text 988. In the UK, call Samaritans on 116 123. Elsewhere, find a crisis line near you . Tell your prescriber the same day.
The label also warns about liver injury: stop and call your prescriber for itching, pain under the right ribs, dark urine, or yellow skin or eyes. Cymbalta should not be prescribed to people with substantial alcohol use or chronic liver disease, the label says. It can raise blood pressure, so the label asks for it to be checked before you start and from time to time after. It can also drop blood pressure when you stand, with dizziness, falls or fainting, most often early on and after a dose increase. Other warnings cover serotonin syndrome, bleeding, low sodium and severe skin reactions. Stopping suddenly because of side effects can bring its own symptoms, such as dizziness, nausea, headache and irritability, and with a half-life of about 12 hours a missed dose can feel like a side effect; talk to your prescriber before stopping. More in Cymbalta withdrawal .
What should you tell your prescriber about Cymbalta side effects?
Tell your prescriber which side effects you have, when they started and whether they are easing. That helps them tell an early effect that will pass from one worth changing the dose or medication for. It helps to tell them:
When you started Cymbalta, your dose and any recent change. Which side effects you have and how strong they are. Whether they're easing, steady or getting worse. What time you take your dose. How much alcohol you drink, and any liver problems. More on doses in Cymbalta dosage .
Download on the App Store Side effects on Cymbalta rise and fade over weeks, and a daily record shows which ones are easing. The withClaro app lets you log mood, sleep, energy and side effects each day, linked to your dose, and turns it into a report for your prescriber.
Frequently asked questions What does Cymbalta feel like at first? Many people notice nausea, dry mouth or sleepiness in the first week, before mood or pain changes. Note what you feel and when, so you can tell your prescriber what came first.
Does Cymbalta make you sweat? Yes, for some people, and it is one of the side effects that tends to stay rather than pass. If it's hard to live with, note when it is worst and tell your prescriber.
Can Cymbalta raise blood pressure? It can. The label asks for blood pressure to be checked before you start and from time to time during treatment. If you have high blood pressure already, mention it before your first dose.
Is Cymbalta hard on the liver? Rarely, it can harm the liver. Across all Cymbalta's placebo-controlled trials, a liver blood test (ALT) rose to more than three times normal in 1.25% on Cymbalta against 0.45% on placebo. The label says it should not be prescribed with substantial alcohol use or chronic liver disease, so tell your prescriber about both before you start.
Related articles
More about Cymbalta Same topic, other medications
Sources CYMBALTA (duloxetine) prescribing information, Eli Lilly and Company, revised August 2023 MedlinePlus: Duloxetine Claro articles are for self-monitoring and educational purposes only. They are not a medical device, therapist, or diagnostic tool, and do not replace care from your prescribing clinician. If you are in crisis, contact your care team, emergency services, the Samaritans (UK: 116 123), or the Crisis Text Line (US: text HOME to 741741).