How to Read a COVID Test: Faint Lines, Positive and Negative Results Explained

What you need to know

Most rapid COVID tests, also called lateral flow tests, show your result as lines next to two letters on the test: C for control and T for test. This guide shows what a positive, negative and invalid COVID test looks like, explains what a faint line means and sets out what to do next. Tests vary between brands, so always follow the instructions in your own kit, including how long to wait before you read the result.

What the C and T lines on a COVID test mean

The C line is the control line. If no line appears next to C, the test is void and the result can't be read, even if there's a line next to T. The T line is the test line: a line next to T as well as a line next to C is a positive result.

Negative line at C only

Positive lines at C and T

Positive faint line at T

Invalid no lines

Invalid no line at C

These diagrams show a typical test. Your test may look slightly different, so check the result guide in your kit's instructions too.

Is a faint line on a COVID test positive?

Yes. A faint line next to T is still a positive result, as long as there's also a line next to C.

What matters is when you read it. Read your result at the time given in your kit's instructions and not after that time has passed. Leaving a test longer than the waiting time in the instructions can affect the result. For example, some tests are read between 15 and 30 minutes and should not be read after 30 minutes.

What does a positive COVID test look like?

A positive COVID test has two lines: one next to C and one next to T. A positive result means it's very likely you have COVID-19. If you test positive:

• try to stay at home and avoid meeting people for 5 days after the day you took the test if you're 18 or over, or 3 days if you're under 18
• try to wait 10 days after the day you took your test before meeting anyone who is more likely to get seriously ill from viruses, such as someone with a weakened immune system
• if you're eligible for COVID-19 treatments, call your GP surgery, NHS 111 or hospital specialist as soon as possible

If you live in England, you don't need to report your result, whatever it is.

What does a negative COVID test look like?

A negative COVID test has one line next to C and no line next to T. A negative result means it's unlikely you have COVID-19. There's still a chance you could have the virus, so follow the NHS advice on how to avoid catching and spreading COVID-19.

If you're eligible for COVID-19 treatments and you still have symptoms after a negative result, do a total of 3 rapid lateral flow tests over 3 days, one test a day.

What does an invalid or void COVID test look like?

A COVID test is void if no line appears next to C. That includes a test with a line next to T but no line next to C. A void result can't tell you whether you had COVID-19 when you did the test. Do another test as soon as possible.

How to get a COVID test result you can read

• Check the expiry date before you start, and don't use an out-of-date test.
• Read your kit's instructions carefully, as it may be different to a test you've done before.
• Follow the kit's instructions on preparing for the test, including washing your hands and blowing your nose.
• Add the number of drops the instructions tell you to.
• Set a timer and read the result at the time the instructions give.

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When to get medical help for COVID-19 symptoms

Ask for an urgent GP appointment or get help from NHS 111 if:

• you're worried about your or a child's COVID-19 symptoms or are not sure what to do
• the symptoms are getting worse or are not getting better
• you or a child have other signs of illness, such as a rash, loss of appetite, or feeling weak
• you or a child have a high temperature that lasts 5 days or more or does not come down with paracetamol
• a child under 3 months old has a temperature of 38C or higher, or you think they have a high temperature
• a child 3 to 6 months old has a temperature of 39C or higher, or you think they have a high temperature

It's particularly important to get help if you're at increased risk of getting ill from COVID-19, such as if you're pregnant, aged 60 or over, or have a weakened immune system.

Call 999 or go to A&E if you or a child:

• seem very unwell, are getting worse or you think there's something seriously wrong – children and babies in particular can get unwell very quickly
• get sudden chest pain
• are so breathless you're unable to say short sentences when resting or your breathing has suddenly got worse – in babies their stomach may suck in under their ribs
• start coughing up blood
• collapse, faint, or have a seizure or fit for the first time
• have a rash that does not fade when you roll a glass over it

A pharmacist can help with a cough. See our advice on coughs, sore throats and colds and flu, or find out about our COVID vaccination service.