Anyone in the UK who has symptoms can apply online via the government website for a free coronavirus PCR swab test, which tells you whether you currently have COVID-19.
You can also get a free rapid lateral flow test if you do not have symptoms.
In addition, private providers are selling private COVID-19 tests to the public, including high street pharmacy chains Boots, Superdrug and Lloyd's pharmacy. There are also many private test providers that have popped up to sell Covid tests for travelling.
But these private tests, which can cost anything from £40 to several hundred pounds, all offer slightly different things - and there are important caveats about what they can tell you, and who should use them.
We explain what you need to know if you want to get tested, including the difference between the types of coronavirus test, what's available and what's legitimate, as well as the limitations of current tests.
Get the lowdown on the different types of tests, how the testing process works and understanding your results:
The PCR swab test, taken from inside the nose and/or mouth, is the main one used by the NHS testing service and indicates whether a person is currently infected with the virus.
The government website urges people to request a test as soon as they develop symptoms, and says testing must be done within the first five days of having symptoms.
If your test needs to be posted, you also need to allow time for it to arrive within that time.
The test involves swabbing the inside of your nose and the back of your throat, using a long cotton bud. You have to do it yourself and it can be unpleasant as the swab needs to go quite deep.
An increasing number of private clinics are marketing coronavirus swab testing services, either via a home test kit, clinician home visit, or clinic appointment (though some won't see you if you have symptoms).
These tests are expensive: they are about £110-160 for a home or in-store test kit and up to £350 for a home visit. Estimates for results turnaround are between 24-72 hours.
You will need to buy a private Covid test if you want one for travel: the free NHS PCR test cannot be used for travel.
To check if you currently have COVID-19:
To check if you previously had COVID-19:
As the name suggests, these tests - also commonly called lateral flow tests - have a quicker turnaround time than PCR tests.
They're also done using a throat or nasal swab, with results available in around 30 minutes.
Some scientists say that these tests have an important role to play in population screening, while others are concerned that false negatives could contribute to a false sense of security. There has been some debate over how well these tests pick up asymptomatic infections when performed at home.
As students return to school across the UK, new testing programmes have been put in place in a bid to detect asymptomatic cases and minimise the spread of the virus.
After in-school testing in the first week, secondary students will be asked to take two rapid tests per week, provided for free (in Scotland, this will begin with senior phase students, with younger secondary students in Scotland will start testing after the Easter break).
Testing is voluntary and requires parental consent, but it's strongly encouraged. Testing is also available for primary and secondary school staff.
Tests can be ordered online or picked up from a collection point.
In England, Scotland and Wales the tests being used are lateral flow tests, done by swabbing the nose or throat. In Northern Ireland, they are lamp (loop-mediated isothermal amplifcation) tests, done with a saliva sample.
Anyone who gets a positive result will need to isolate, and confirm the result with a PCR test.
There have been some concerns raised about the accuracy of rapid Covid tests, as the false negative rate has been shown to be high - though it's hoped that this could be mitigated with repeat testing.
But there are also worries about the impact of students having to isolate unnecessarily if they get a false positive result.
NHS advice says you do not need to isolate if you receive a negative result, as long as everyone in you household or support bubble with symptoms also tests negative, and if you haven't been told to isolate by NHS Test and Trace.
Some doctors have raised concerns about the false negative rate for coronavirus testing, where your test is negative but you do actually have the virus, leading to possible false reassurance.
It is not known what the rate of false negatives is (a report in the British Medical Journal estimated it is between 2% and 29%), but a negative result from a swab test is conveyed to patients in very definitive terms - 'you did not have the virus when the test was done' - without any information about what might affect the result or its accuracy.
Government advice does tell people to continue isolating if you're feeling unwell, even with a negative test result, so if you're unsure, it's best to stay at home.
There are also worries about the lack of information about an inconclusive test result, with patients simply being told their test is unclear and to apply for another one, but no information as to why this might be or how to avoid invalidating the test on another try.
If you receive an unclear result and you have symptoms, you must self-isolate for 10 days from the onset of symptoms, but if you don't, you don't have to self-isolate.
Anyone in your household or support bubble must also self-isolate for 10 days either from when your symptoms started or from when you got your result if you're asymptomatic.
In England and Wales, you should be contacted by NHS Test and Trace after testing positive. In Northern Ireland, you will be contacted by the PHA Contact Tracing service, and in Scotland, you'll be contacted by the National Contract Tracing Service.
If you've had a positive result from a lateral flow - or rapid - coronavirus test, you need to take a PCR test to confirm the result.
The testing and tracing systems operate under slightly different guises across the UK. These are:
The basic steps for the testing and tracing systems operating across the UK are:
Share contacts: if you get a positive result, you will be contacted with instructions of how to share details of people with whom you have had close, recent contact and places you have visited.
Antibody tests are meant to show whether a person has already been infected with coronavirus. They work by detecting the presence of the antibodies our bodies produce to kill the virus.
Expanding accurate antibody testing would help experts understand how far the virus has spread, and how many people might have had it asymptomatically, or with mild symptoms.
They are currently being rolled out to health and social care staff, patients and care home residents on a trial basis.
Antibody tests are measured on specificity - which measures the proportion of 'true' negatives - and sensitivity, which measures the proportion of 'true' positives,
Jon Deeks, Professor of biostatistics at the University of Birmingham, says that while a positive result is fairly definitive, a negative result is less certain.
Professor Deeks explains that antibodies might not present as strongly in people with mild or no symptoms and studies so far have mostly been done on patients with severe cases - so this could skew the data for how accurate the tests are.
Antibody tests, which identify if you've previously been infected with COVID-19, are available to buy from a range of private providers - most commonly they require a blood sample which is taken by a healthcare professional.
Antibody tests where you take your own blood sample with a home finger-prick test and send it to a lab for analysis were banned for a period of time, while the sampling process was being investigated by the Medicines and Healthcare Products Regulatory Agency (MHRA) to see whether it's viable.
Superdrug has now relaunched its home fingerprick antibody test, which it says it compliant with the evolving MHRA guidance. The test is available through Superdrug's online doctor service and costs £69.
The MHRA warns that 'anyone using a sample collection kit to test for COVID-19 must read the instruction leaflet carefully. It is very important that you have a clear understanding of the process because if the sample is not collected properly, the result may not be accurate.'
Other private health companies such as Qured, Medichecks, DocTap and Forth are offering to send a healthcare worker to your house to administer the test, or selling antibody tests along with an in-person doctor's appointment. This generally costs about £85-£130 per test.
We don't think it's worth spending money on an at-home coronavirus antibody test currently, as there's a risk that they could give a false sense of security, and they can't tell you much right now on an individual level.
Self-test coronavirus kits - where you take the test and read the results yourself at home - are not approved for sale in the UK and any company selling these is doing so illegally.
It's important to note that you should continue to follow government advice around social distancing regardless of an antibody test result.
It is hoped that once someone has had COVID-19, they are immune to the disease, but crucially, this is still uncertain.
The presence of antibodies in your blood can tell you you've been exposed to the virus, and therefore can also offer some information about how you reacted to it, but at the moment that's about it.
The World Health Organisation (WHO) says: 'We expect that most people who are infected with COVID-19 will develop an antibody response that will provide some level of protection. What we don't know yet is the level of protection or how long it will last.'
It warned against making assumptions about a person's immunity to coronavirus based on antibody testing. A positive result can't yet be interpreted as a stamp of immunity, and there have been some suspected incidences of reinfection.
Any level of immunity can only be assumed in the short term because we just don't have long-term data yet on how this virus behaves.
The Advertising Standards Authority (ASA) has banned some advertising from private clinics including the London Vaccination Clinic, Solihull Health Check Clinic and the Corona Test Centre London for claiming that a positive antibody test would show that people were immune to the disease.
Antibodies are also not the only way to gauge immunity from a disease. T-cells (a type of white blood cell) also play a role in the body's immune response by mobilising the body's defence mechanisms and destroying infected cells.
Researchers have discovered a T-cell response to coronavirus in people who didn't have antibodies, but more research needs to be done in this area.
Story last updated: October 2021 This story was originally published in March 2020 but has been regularly updated to reflect new information and rules around testing.