Only one GP is on call to cover 370,000 patients during part of the night in mid Essex.
Two doctors are on call for the area, which includes Braintree, Chelmsford and Maldon districts, every night until midnight, dropping to one between midnight and 8am.
But health bosses say they are supported by a team of clinicians and the number of out of hours calls is very low.
Dr Donald McGeachy, medical director for NHS North Essex, which covers mid Essex, said: “There is a network of urgent care and emergency services to respond to clinical needs out of normal service hours for the people of mid Essex.
“Frontline services include a 24 hour district nursing team, mental health crisis teams, emergency dentists, emergency pharmacists, on-call social workers, ambulance paramedics and an on call midwifery team."