GPs in England are being urged to delay non-urgent blood tests in response to a global shortage of collection tubes.
NHS England issued guidance asking doctors to focus on high-priority testing and reduce non-clinically urgent procedures such as routine wellness screening and vitamin D and allergy testing.
The recommendations – which are also aimed at medical and nursing directors and pathology laboratories – have been drawn up by a panel of clinical experts from the fields of pathology, primary care and acute care.
NHS England said there were "global shortages of blood tube products", not just with its suppliers Becton Dickinson (BD), and that guidance was being issued "in order to balance demand". It said work is ongoing with the Department of Health and Social Care (DHSC), NHS Supply Chain and BD to resolve the issue.
In the meantime, doctors are being advised that changes to patient testing should be made in consultation with individual patients.
The guidance said: "It is important to make clear that tests that have been deferred will be carried out in the future where appropriate. As part of conversations with patients it is important to make clear that routine tests will be deferred only where it is clinically safe to do so."
Concerns have been raised that delaying blood tests will exacerbate existing treatment backlogs.
Deputy chair of the BMA Dr David Wrigley warned of the impact delaying testing could have on regular tests for NHS health checks, the monitoring of quality of care, and medication reviews.
He added: "It would also be unreasonable to ask healthcare staff to simply delay these tests until a later date – not only for the sake of our patients, but also the entire system, which is already tackling an enormous backlog of care."
A DHSC spokesperson told the BBC: "Patient safety and continuity of care is our priority and we are working to ensure there is minimal possible impact on patient care.
"The health and care system is working closely with BD to put mitigations in place to resolve any problems if they arise," they added.