Lateral flow home test kits are unavailable on the Government website, as people wait to book a coronavirus vaccine.
The Government website on Monday said “there are no more home tests available”.
It advised people to “try again later” or to book a test site appointment instead.
One person said on Twitter: “Tried to order a lateral flow test kit and the NHS site says they have no more! What’s going on!”
However, there appeared to be no problems with the availability of PCR home test kits.
It comes as people trying to book a Covid-19 booster jab in England have been advised by the NHS to try later or tomorrow as people faced a queue on the website.
It comes a day before fully vaccinated people are told to take a lateral flow test every day for a week if they come into contact with someone infected.
From Wednesday, partygoers will also be required to display vaccine passports or a negative lateral flow test to enter clubs or large venues.
Christmas shoppers and anyone else visiting crowded spaces have been urged to do lateral flow tests beforehand too.
In a tweet, the NHS said: “The Covid vaccine booking service is currently facing extremely high demand so is operating a queuing system.
“For users aged 18-29, please be aware that booking opens on Wednesday 15 Dec. For all others experiencing waits, we would advise trying again later today or tomorrow.”
It comes on the first day that 30 to 39-year-olds in England can officially book the jab.
The service had already booked more than 140,000 vaccine appointments on Monday, NHS Digital said, with people waiting several minutes.
The PA news agency has approached UK Health Security Agency (UKHSA) for comment.