Many junior doctors do not understand common hospital laboratory tests and are putting patients at risk as a result, biochemists have claimed.
The majority of tests are ordered by junior doctors
The Annals of Clinical Biochemistry reports that 18% of more than 80 junior doctors surveyed were happy to order a test they could not fully interpret.
The Association for Clinical Biochemistry blamed poor teaching of the subject at medical schools.
The General Medical Council is planning to review its curriculum guidance.
The majority of hospital pathology tests are ordered by junior doctors, but in recent years many medical schools have reduced the amount of time they devote to pathology teaching.
Dr Trevor Gray, from the Northern General Hospital in Sheffield, carried out a survey of more than 80 juniors, asking them how they felt about the clinical biochemistry tests they were expected to order on a day-to-day basis.
In 10 out of the 12 common tests listed, some of the juniors questioned said they were not entirely confident about interpreting the results.
In three tests, more than a third of those questioned said they were not confident - and 18% of the doctors said they were happy to order a test which they did not fully understand how to interpret.
Seven out of 10 said they would like more teaching in clinical biochemistry.
Dr Danielle Freedman, from the Association of Clinical Biochemistry, said the results revealed "a national problem".
"It's something that scares me - these are the doctors who are going to be looking after me when I'm older."
She said that errors could be highly dangerous to patients: "If you have someone who has a test which shows they have a low sodium level, further tests need to be done to establish the cause.
"Some junior doctors can order the sodium test, but don't know what to do with the result, and the patient doesn't get the right treatment."
She said that she knew of patients who had been discharged from hospital only to suffer a major heart attack because a key test had not been carried out properly.
The General Medical Council (GMC) is currently preparing to review its guidance on the content of medical education.
"It is essential that the GMC, universities and medical school take note to protect both patients and doctors," Dr Freedman said.
Among those responsible for pathology teaching in UK medical schools is the Royal College of Pathologists, and a spokesman said that it was currently examining what medical students were taught.
"The college has set up a group to review and appraise the new curriculum."