The NHS is failing to deliver proper care to 852,000 diabetics in England - 60% of the total - according to an audit by the NHS Information Centre.
Vital checks recommended by the National Institute for Health and Clinical Excellence (NICE) for cholesterol, blood-sugar levels and body mass index are not being carried out, it says.
The failure mostly involves those with type 1 diabetes, which is usually diagnosed in childhood, although type 2 diabetes - linked to unhealthy lifestyles - is included.
Meanwhile, the number of diabetics suffering from complications is subject to wide regional variation, with stroke, heart attack and kidney failure more likely in some parts of the country than others.
NICE lays down nine sets of checks, including eye and foot examinations, blood pressure and cholesterol tests, glucose monitoring and smoking history.
The audit reports a study showing that patchy care offered by GPs and hospitals in 2007/08 means that people with type 1 generally fare worse across key areas than those with type 2.
"I don't agree with the statements above. My wife has been type 1 diabetic for 40 years (now 75) and has had excellent treatment throughout by our NHS. She sees her NHS consultant every four months, has all her insulin and the latest injection pens provided free by the NHS. She has had twice in recent years to be admitted with complications with her condition - a week in hospital each time immediately arranged by our GP who sent the ambulance - all at no cost to us at the point of need. I paid in to the NHS quite painlessly for 40 years as part of my monthly taxes rated to earnings but capped. My wife has not paid a penny into the service. The NHS is 60 years old and we have benefited mightily from having it as a nation and as a family. The NHS satisfaction level has been tested by independent pollsters since early days. Last year it was 83% - how many other organisations anywhere can claim that? OK there are grumbles and failings - any outfit employing 500,000 staff and with a nearly $200 billion annual budget must have backsliders - but boy do we thank our lucky stars every waking day that our fathers' generation set it up. Wake up America and join the 500 million in the European Union - all 27 countries have similar state schemes which as British citizens we can (and have in France and Spain) access" - Brian Morris, Andover