Type 2 is the most common form of diabetes
People with diabetes are suffering needlessly from regular low blood sugar attacks, a survey suggests.
Among 2,000 people with type 2 diabetes, half had experienced symptoms of a hypoglycaemic episode in the past two weeks, the study found.
GPs said increasing pressure to tightly control patients' blood sugar was partly to blame for the problem.
Diabetes UK, which commissioned the survey, said it suggested many patients may not be on the right medication.
The number of people diagnosed with diabetes in the UK has increased by more than 145,000 in the last year, bringing the total figure to 2.6 million, the latest figures show.
A key part of treatment is to make sure blood sugar levels do not get too high, because this can lead to severe complications in the long term.
But on the other hand, very low blood sugar is also dangerous.
One type of commonly used drug in type 2 diabetes - sulphonylureas - can lead to hypoglycaemia, experts said.
The latest survey focused on mild or moderate attacks, which often come with warning signs such as feeling shaky, sweating, tingling in the lips, going pale, heart pounding, confusion and irritability.
More than half of those questioned said mild to moderate "hypos" affected their quality of life and one in 10 reported having to take at least one day off work in the last year as a result of a mild to moderate attack.
One third reported that mild to moderate hypoglycaemic attacks affected their ability to carry out day-to-day tasks, including housework, social activities, sports activities and sleep.
Causes of a hypoglycaemic attack include taking too much diabetes medication, delayed or missed meals or snacks, not eating enough carbohydrate, doing more exercise than usual and drinking alcohol without food.
People having regular attacks may stop having warning signs and pass out without realising anything is wrong.
Those taking part in the research were not taking insulin, which can also cause hypoglycaemia.
Simon O'Neill, Diabetes UK Director of Care, Information and Advocacy, said: "We want to see hypos become the exception rather than the rule."
Dr Brian Karet, a GP in Bradford and a medical advisor for Diabetes UK, said the figures in the survey seemed high but he agreed there was a lot of hidden hypoglycaemia.
"It is a lot more common than is often recognised especially these days when we are encouraged to put people on multiple medications.
"The modern sulphonylureas are actually quite powerful and if they are prescribed along with other drugs this is going to be an increasing problem."
He said anyone having regular symptoms should get checked out and they might need better advice on managing their condition, or they might need a lower dose of medicine.
Professor Mike Pringle, a GP in Nottinghamshire, and an advisor on the original National Service Framework for Diabetes, said the findings were "surprising".
"If they are confirmed it does suggest we may be overtreating these people.
"They are obviously learning how to manage their symptoms, but it is not intended they have these symptoms.
"There is a balance we need to strike and we need to better understand this information."