The symptoms are different in everyone and many people there may be NO symptoms at all.
The most common symptoms in
Women:
Increased vaginal discharge
Bleeding after intercourse or inbetween periods
Pain or discomfort on passing urine
Lower abdominal pain
Pain internally during intercourse
Anal discharge

Men:
Discharge from the penis
Pain or discomfort on passing urine
Anal discharge

It is an important condition to treat as it could lead to serious complications if left untreated:
Women
Pelvic inflammatory disease (PID) , endometritis, salpingitis
Tubal infertility
Ectopic pregnancy
Sexually acquired reactive arthritis
Perihepatitis

Men
Sexually aquired reactive arthritis
Epididymo-orchitis

The more commonly seen side effects with these medications include:
Doxycycline:
Allergic reaction
Diarrhoea, nausea or vomiting
Headache;
Purple rash: Henoch-Schönlein purpura
Sensitivity to sunlight;
Azithromycin:
Abdominal discomfort
Diarrhoea, nausea or vomiting
Dizziness;
Headache;
Hearing problems
Insomnia;
Pancreatitis;
Skin reactions;
Please see the attached patient information leaflef for the full list of possible side effects

You can have this done free on the NHS. Options include walk-in and prebookable appointments, or even just having a self-test kit posted to you. Click here (https://www.nhs.uk/service-search/sexual-health) to find a clinic near you.

It is absolutely vital that any previous partners are told if you have chlamydia. Chlamydia often doesn't cause any symptoms, so previous partners may not have any warning that they should get tested. But don't worry if this seems daunting! If you contact a local sexual health clinic, they are usually happy to make the calls for you. See the link above for contact details.