When is the best time of day to take citalopram?

Fun fact, celexa, unlike its cousin lexapro, has some antihistamine properties (like benadryl). So it's actually pretty common to take celexa at night because it can be a little sedating. It may take a few days to adjust to the change though.

Hi Beeching-
Masso is right that in some people taking it at night can cause insomnia.
You can try taking it at night to see if you can sleep through the side effects. If not, you can always go back to the daytime dose.
Hope it all works out for you.

Yes, ADs (SSRIs) are usually taken in the morning as most can cause insomnia in some people.

Psychiatric
Very common (10% or more): Insomnia (up to 18.8%)
Common (1% to 10%): Abnormal dreams, aggravated depression, agitation, anxiety, apathy, confusion, depression, impaired concentration, nervousness, suicide attempt, sleep disorder
Uncommon (0.1% to 1%): Aggressive reaction, delusion, depersonalization, drug dependence, emotional lability, euphoria, hallucination, mania, panic reaction, paranoid reaction, paroniria, psychosis, psychotic depression
Rare (less than 0.1%): Catatonic reaction, melancholia, suicide-related events
Frequency not reported: Bruxism, restlessness, panic attack, suicidal ideation/behavior
Postmarketing reports: Delirium, withdrawal syndrome.

https://www.drugs.com/sfx/citalopram-side-effects.html