Your GP should be able to diagnose conjunctivitis by asking about your symptoms and examining your eyes.
Describing how your conjunctivitis started can help your GP diagnose which type it is and decide whether it needs to be treated.
The most common symptoms of infective conjunctivitis are sticky, red and watery eyes. However, infective conjunctivitis can sometimes be confused with other types of conjunctivitis, which are treated differently.
Your GP may suggest further tests, such as a swab test, if your conjunctivitis hasn't responded to treatment, or to help decide what treatment to use.
A swab looks similar to a cotton bud. It's used to collect a small sample of mucus from your infected eye, which is sent to a laboratory to find out the cause of your conjunctivitis.
If your symptoms are severe or don't respond to treatment, you may need to see an eye specialist (ophthalmologist).
Most cases of conjunctivitis clear up within one to two weeks without needing any medical treatment. In some cases, it can last for longer than two weeks, which is known as persistent infective conjunctivitis.
If you have any unusual symptoms, such as severe pain, blurred vision or sensitivity to light, it may mean that you have a more serious condition.
If you have any of these symptoms, it's very important to seek medical assistance immediately, either by contacting your GP or going to your nearest hospital.
Other more serious conditions include:
Contact your GP straight away if you think your baby may have infective conjunctivitis (also called neonatal conjunctivitis).
If this isn't possible, call NHS 111 or your local out-of-hours service. Your GP will examine your baby closely to see if they have sticky eyes or infective conjunctivitis.
All newborn babies with infective conjunctivitis must be referred to an eye specialist straight away for treatment.
Read more about the symptoms of infective conjunctivitis.