Thousands of people every year are suffering severe sepsis or dying from the illness due to NHS failures, a report has found.
GPs and hospital doctors are failing to spot signs of sepsis - which kills at least 37,000 people a year in the UK - and are diagnosing the condition too late, experts said.
Even when sepsis was suspected, a treatment regime to bring it under control was not always implemented quickly.
The review - from the National Confidential Enquiry into Patient Outcome and Death (NCEPOD) - said there are an estimated 200,000 cases of sepsis a year in the UK.
It is a leading cause of avoidable death in the UK, and kills more people than breast, bowel and prostate cancer combined.
Sepsis occurs when the body is overwhelmed by infection, which can lead to organ failure and death.
In one third of the cases reviewed by NCEPOD where a GP saw the patient, not one of the four basic vital signs of temperature, pulse, blood pressure and respiratory rate had been recorded.
When patients were sent in to hospital, no referral letter from the GP was available in 43% of cases.
The experts said GPs managed patients properly on the last visit before the patient went into hospital, but there were failures on previous visits, including an over-reliance on speaking to patients on the phone.
The report said: "On the previous two visits, more patients received less than adequate management in terms of their assessment, monitoring and treatment.
"Areas of deficiency included the recording and monitoring of vital signs, maintaining adequate and legible records, delayed referrals, and relying on a telephone consultation, resulting in missed clues on diagnosis and severity.
"A thorough clinical assessment should have been done in person."
Overall, sepsis was missed by GPs in 28 (36%) out of 77 cases studied in detail, and in a quarter (19 out of 72), the severity was underestimated.
Things were not much better for patients diagnosed with sepsis in hospital, with 40 of 279 patients not having a timely review by a senior clinician.
Some 18% of patients did not have vital signs recorded in A&E and a possible source of infection was only recorded at triage in 148/321 (46%) of patients admitted via A&E.
Some patients developed sepsis in hospital. In 10/88 (11.4%) of these patients, experts concluded the infection was preventable.
Some 24% of these patients could have had their infection identified sooner and 37% should have had their treatment started sooner, the report said.
There was a delay in identifying sepsis in 182 out of 505 (36%) cases, severe sepsis in 167 out of 324 (52%) cases and septic shock in 63 out of 193 (33%) cases.
Investigations considered essential in the diagnosis of sepsis were missed in 198 out of 506 (39%) patients and delayed in 190 out of 496 (38.3%).
Dr Alex Goodwin, author of the report, said: "Sepsis has a number of faces. In some cases it can be very obvious in patients who have low blood pressure, a high temperature, racing pulse or altered mental state.
"But, it can also be present without any of these symptoms, and is commonly mistaken for flu.
"This is why it can be so difficult to diagnose, and why recording a patient's vital signs at all stages and documenting sepsis is so important."
Dr Vivek Srivastava, report author, added: "I am very concerned about the serious lack of awareness of sepsis, and the reliance on the experience of senior hospital clinicians to diagnose it."
Dr Srivastava said treatment was simple, cheap and readily available.
"Taking a blood culture, giving antibiotics, oxygen and intravenous fluids requires a fraction of the resources needed when compared with a hyperacute stroke unit for example, and are well within the competence of junior doctors."
A spokeswoman for NHS England said: "Recognising the signs of sepsis and treating it early saves lives, and we want the NHS to be the safest healthcare system in the world.
"We are constantly working to improve care and NHS England will shortly be publishing an action plan to support healthcare professionals to recognise and treat sepsis."