While citalopram is generally considered to be well-tolerated, there are some potential side effects that can be more serious and cause significant distress or impairment. These are considered to be the “worst” side effects of citalopram and can include:

Suicidal thoughts: One of the most concerning side effects of citalopram is an increased risk of suicidal thoughts and behavior, especially in young adults under the age of 25. If you or someone you know experiences any thoughts of suicide while taking citalopram, it is important to seek immediate medical attention.

Serotonin syndrome: Citalopram works by increasing the levels of the neurotransmitter serotonin in the brain. In rare cases, citalopram can cause a condition called serotonin syndrome, which is characterized by symptoms such as high fever, rapid heart rate, muscle rigidity, and confusion. If you experience any symptoms of serotonin syndrome, it is important to seek medical attention immediately.

Allergic reactions: Some people may experience an allergic reaction to citalopram, which can cause symptoms such as itching, hives, and difficulty breathing. If you experience any symptoms of an allergic reaction, you should stop taking citalopram and seek medical attention immediately.

Seizures: Citalopram can rarely cause seizures in some people, particularly in those who have a history of seizures or a condition that increases the risk of seizures. If you experience a seizure while taking citalopram, you should seek medical attention immediately.

Abnormal bleeding: Citalopram can increase the risk of abnormal bleeding in some people, particularly if they are taking other medications that affect blood clotting. If you experience any unexplained bleeding or bruising while taking citalopram, you should contact your healthcare provider for further evaluation and treatment.

Mania: In some cases, citalopram can cause manic symptoms such as increased energy, decreased need for sleep, and grandiose ideas. If you experience any manic symptoms while taking citalopram, you should contact your healthcare provider for further evaluation and treatment.

Interference with other medications: Citalopram can interact with other medications and cause potentially serious side effects. For example, citalopram can interact with blood thinners and increase the risk of bleeding, or with monoamine oxidase inhibitors (MAOIs) and cause serotonin syndrome.

It’s important to note that these side effects are relatively rare and most people do not experience any serious side effects when taking citalopram. However, it is important to be aware of the potential risks and to seek medical attention if you experience any concerning symptoms while taking citalopram.