Hospitals and GPs in England are being forced to ration blood tests as the NHS struggles to cope with a severe shortage of the plastic sample bottles that are then sent to a laboratory for analysis.

Some GP surgeries have stopped giving patients routine blood tests to assess the health of those with heart disease, high blood pressure and diabetes. In some places, GP practices have had to ring patients to tell them not to come in for pre-booked blood tests as a result of the problem.

Hospitals are also telling GPs in their area to cut back on the number of tests they do by more than 50% to try to conserve supplies, stocks of which are running dangerously low in many places.

The medical director of an acute hospital trust in Hampshire told colleagues in an email that although it had cut blood tests by 16%, a “further and dramatic” contraction “across the board” is still needed because “the shortage in supply is a 60% reduction” on usual stocks.

GPs have told the Guardian that they expect to run out of blood bottles altogether next week. NHS England and the Department of Health and Social Care (DHSC) are urgently trying to obtain extra supplies. But some doctors fear the shortage is set to last until nearly the end of the year.

NHS England has already told doctors to stop testing in “non-clinically urgent” cases involving allergies, vitamin D levels, “routine wellness”, including pre-diabetes and high levels of cholesterol and also infertility, except for women over 35, until the “supply disruption” is resolved. That was in guidance issued on 10 August that said the suspension of such tests was to ensure urgent care was not disrupted.

It has highlighted “global shortages of blood tube products” and told GPs and hospitals at risk of running out of supplies within 48 hours to let them know so that extra supplies can be arranged.

Doctors are worried that the sudden restrictions could lead to diseases being diagnosed late, which could make treating patients harder and their outcome more uncertain.

The problem has arisen because Becton Dickinson, which provides most of the blood collection tubes used by the NHS in England, can no longer supply anywhere near its usual quantities. It has blamed an unprecedented demand caused by the large number of people being tested for Covid-19 and the testing of people whose treatments have been delayed due to the pandemic disrupting NHS services.

One GP in Bristol said: “Our supplies will run out by next week and we don’t know what will happen next. Blood tests are only being done now on a strictly very urgent basis.

“All low-level bloods are not being done, such as annual clinic bloods for blood pressure, heart disease and diabetes reviews.

“Each blood test that has already been booked is being looked at by our nurses. Any [blood test] specifically requested by the doctor in surgery or hospital is being passed back to the GP to check if [it’s] really needed.”

The shortage has created “a level of risk” for the GP, her colleagues and their patients as they may not be able to diagnose illness because, under pressure to cut back, they weren’t able to order a test. It could lead to late detection of conditions such as diabetes, thyroid disease and anaemia, she added.

Karen O’Reilly, a GP in Hampshire, said: “This is a huge problem. We as doctors are very worried about how this will affect patient care and patient safety. Panic-stricken may be a slight exaggeration – but, in the absence of accurate information and transparency about the situation, it’s not far-off.

“There is a concern that our supplies [at the surgery] may run out in about 10 days. If we run out of bottles, I presume so will hospitals. I can’t envisage a health service functioning safely without access to haematological and biochemical tests.”

Dr David Wrigley, the deputy chair of the British Medical Association’s ruling council, said: “While NHS England has provided some guidance for clinicians to follow, no doctor wants the consequence of delayed diagnosis for patients due to these shortages.”

A Becton Dickinson spokesperson told the BBC it was facing logistical obstacles in its manufacturing capacity, including shortages of raw materials and transport problems. They added: “We are balancing the frequency of preventive maintenance leading to plant shutdown to provide a continuing supply of products, and we are working closely with our raw material suppliers, transport agencies and other necessary third parties to minimise supply disruptions.”

NHS England and the DHSC have been approached for their responses.