On 40mg celexa for a month. only real side effect is drowsiness. will it last the entire time i take the meds? or will it subside with time.

Can not say for: sure. However, if my patients experience sedation on it - I normally encourage them to take it before bed. Discuss with your prescribing provider.

Often goes away: In many cases, the drowsiness does tend to diminish with time. However, this is individualistic; you should speak to your doctor and be followed closely to determine if this side effect continues to be an issue.