Duloxetine is used to treat depression and anxiety. In addition, duloxetine is used to help relieve nerve pain (peripheral neuropathy) in people with diabetes or ongoing pain due to medical conditions such as arthritis, chronic back pain, or fibromyalgia (a condition that causes widespread pain). Duloxetine may improve your mood, sleep, appetite, and energy level, and decrease nervousness. It can also decrease pain due to certain medical conditions. Duloxetine is known as a serotonin-norepinephrine reuptake inhibitor (SNRI). This medication works by helping to restore the balance of certain natural substances (serotonin and norepinephrine) in the brain.