It has become very clear that there are nowhere near enough lateral flow tests for Covid-19 in England to allow the government’s policy of their indiscriminate use. Even if funding could be found to buy more tests, it is unlikely that the government could source enough tests to meet current and future demand because of the many other countries that are also trying to obtain the tests as they struggle to control the wave of infections from the Omicron variant. The government is in part to blame for the current problems with the increased demand for tests. It has encouraged members of the public to test regularly. For example, before social events such as parties and also before meeting friends and family from outside their immediate household. The very high level of Covid-19 cases in the UK (with around 183,00 cases reported on 29 December) also means that many more people will have been advised to test regularly in line with guidance from Test and Trace. This will include guidance for close contacts of cases who are asked to carry out daily tests for 10 days if they are fully vaccinated and want to avoid isolating. People with a Covid-19 infection can also test themselves on day six and day seven of their illness, and end their period of isolation if they are asymptomatic and the two tests are both negative. What can we do to improve how well lateral flow tests are used? The first step is for the government to publish data on the daily supply of tests. We then need clear guidance from the government on what groups should be prioritised for testing and how frequently they should test. Carrying out several tests in one day is not a good use of these tests. Nor is carrying out daily lateral flow tests after a positive PCR test (other than on day six and seven, as discussed above). Even daily tests are inappropriate in asymptomatic people when there is now such a large gap between the supply and demand for tests. NHS guidance is for staff to test twice a week with a lateral flow test, but many asymptomatic people are testing more frequently than this. NHS trusts and general practices need to review their testing polices and give clear guidance to staff to protect the supply of tests. Once we have information on the daily supply of tests, we can then prioritise who will have access to these tests. This kind of prioritisation is quite normal in healthcare and was done, for example, with Covid-19 vaccination to ensure access was given based on clinical and occupational priority. Groups for priority access to tests should include: NHS staff in patient-facing roles; teachers and other people working in schools; workers in essential parts of the economy such as public transport; and groups such as HGV drivers to ensure that deliveries of essential items continues. It should also include patients who are clinically vulnerable and those following guidance from Test and Trace. We are also facing a shortage of PCR tests and an important question arises for the government: should we use lateral flow tests to give better access to testing for people with symptoms and reduce testing for people who are asymptomatic? If this does happen, we will still need to decide which groups have access to lateral flow tests in place of PCR tests. But successful implementation of this policy could allow many more people to receive a test. Although lateral flow tests are not as sensitive as PCR tests, they will still identify many people with Covid-19. We need to look again at the costs of supplying these tests and to determine what we can afford to spend. Although the tests are supplied at no cost to the public, they are not free and will come at a considerable cost to the taxpayer. Access to diagnostic services and other health services always has to be limited; and based on factors such as clinical need, health outcomes, and cost-effectiveness. With the country facing record numbers of people with Covid-19, it is important to maximise the benefits of England’s testing capacity. We need the government to act quickly, decisively – and rationally. Azeem Majeed is a professor of primary care and public health at Imperial College London