Drug users may not dial 999 in emergencies or give full information to doctors and nurses who treat them because they fear potential criminal prosecution, a report said.
The British Medical Association (BMA) said the medical profession does not condone drug-taking but warned of users not seeking medical help when they need it, as they are criminalised in current drugs policy.
The report said drugs policy does not have an adequate focus on health, and it called for addicts to be treated like those who have any other illness.
Currently, users may be discouraged from approaching drug services, contacting paramedics in emergency situations or volunteering accurate or complete information to health professionals because they fear policies are mainly focused on criminal justice, the BMA said.
The report also pointed out "a widely held view within the drugs field that the current legal framework has failed to deliver its intended goals of reducing illicit drug use". And it said doctors should have a key role in "refocusing the debate" and influencing global drug policy.
The report concluded drug dependency is a medical condition as well as a legal problem and that alternatives to the current approach to UK drug policy should have health at the centre of the debate.
Professor Averil Mansfield, chairman of the BMA's board of science, said: "The BMA believes that drug users are patients first. That's why we want health to be at the heart of the debate about drugs policy. We fear that too great a focus on criminalisation is deterring drug users from seeking medical help.
"While the medical profession would never condone illegal drug-taking, we believe that we should show understanding of the illness of drug addiction and respond in the way that we would with any other medical problem. We welcome the downward trend in drug use, but it is extremely worrying that long-term problem drug use and drug-related deaths are not decreasing."
Drug addiction is an extremely complex issue and genetic make-up and social circumstances play a fundamental role, the report said.
Prof Mansfield added: "Effective drug policy should take account of the complex biological, psychological and social factors involved in illegal drug use. It is also vital that medical training should provide doctors with the basic knowledge about these factors to help clinicians identify patients at risk. There is no one size fits all answer. Drug addiction cannot be seen in isolation. An individual's social circumstances play a key role in addiction and therefore a holistic approach to treatment is vital."