A national shortage of test tubes for blood tests will "pile further pressure on already beleaguered GPs" and mean patients face the risk of having their test cancelled or delayed.
The British Medical Association has warned that shortages across hospitals and GP surgeries were "severe" and if the NHS did not reduce usage in the coming days "even the most clinically important blood tests may be at risk".
And this feeling has been echoed by GPs in the region, with Tim Morton, chairman of the Norfolk and Waveney Local Medical Centre warning that it could see a knock-on effect across GP services.
He said: "It is hugely frustrating.
"My GP colleagues are faced with extraordinarily difficult decisions over who to prioritise for blood tests and it will cause significant difficulties with chronic disease management for several months, at a time when clinical work is already at an all time high.
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"It is going to put further pressure on our already beleaguered GP workforce."
The shortage is expected to have a particularly detrimental effect on how GP surgeries manage chronic diseases, with diagnoses often dependent on blood tests.
And with the way practices manage chronic diseases being an important target for securing NHS funding, a slowdown in meeting this could have serious knock-on effects across the services.
In Norfolk, several practices have already informed patients of changes forced on them by the vial shortage, including Drayton, Attleborough and the Windmill Surgery in Wymondham.
Dr David Wrigley, BMA council deputy chair, said: "This crisis has put doctors and their patients in a terrible, unenviable position.
"No doctor knowingly undertakes unnecessary blood tests and to now have to ration all those we are doing, as well as cancel hundreds more, goes against everything we stand for as clinicians.
A Department of Health and Social Care spokesperson said: "Patient safety is a top priority and we are working closely with NHS England, the devolved administrations, and NHS Supply Chain to minimise any impact on patient care.
"The health and care system continues to work flat out with the supplier and stakeholders to put mitigations in place, and restore normal supply, and there continues to be stock in place."
What have local surgeries said?
Drayton Medical Practice warned patients it may have to cancel existing bookings - and that they will be contacted if they need rescheduling.
The Attleborough surgeries said they will be reviewing pre-booked appointments daily and will not be offering routine appointments for the coming days.
The Windmill Surgery in Wymondham said it would honour any tests already booked in but going forward would only offer urgent tests until the problems are resolved.
The same was announced by the Hingham Surgery.
The Humbleyard Practice in Cringleford said it would review all required blood tests to see which could be delayed safety. It will also continue to add to a waiting list for tests.
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