People are losing their jobs because they have diabetes, a BBC Five Live investigation has found.
Ambulances are among vehicles which people with diabetes may not be allowed to drive
A taxi driver and a cake factory worker are among those whose employment was affected by their illness.
Firefighters and ambulance drivers have also reported that their jobs were being affected.
Campaigners say that is unacceptable that people are barred from jobs, and are fighting to bring an end to the discrimination.
Liz Morrison, who has diabetes, was sacked from Emma's Country Cakes in Coleford, Gloucestershire.
Her dismissal was triggered by her being seen drinking a can of Coke to boost her blood sugar.
Her case was recently settled out of court. The company has declined to comment.
In another case, the Employment Appeals Tribunal upheld a ruling in 2004 against BT under the Disability Discrimination Act in which Mr J Pouson, a diabetic call centre worker, was discouraged from leaving his desk to test his blood sugar levels because he would fail to meet performance targets.
When he tested himself at his desk, he offended his colleagues.
As a result he was reluctant to test himself and suffered a hypoglycaemic attack in August 2001. This caused him to fall and hit his head.
He sustained a subdural haemorrhage and never returned to work with BT.
And Pat Flynn had her taxi licence revoked by her council when she switched from taking tablets to insulin injections.
Now legally back behind the wheel of her cab, she reflects on the bizarre inconsistencies in the law.
"I couldn't drive on insulin in Newbury, but if I moved 30 miles down the road to Bracknell, I could have driven there."
She says: "The main problem for diabetics is other people's ignorance."
By law, an employer cannot refuse to employ or dismiss someone, purely because of their diabetes. Only the armed forces are exempt.
Douglas Smallwood, chief executive at Diabetes UK said: "It is unacceptable that many people who treat their diabetes with insulin, who are perfectly fit to drive, are still denied a livelihood.
"We believe that judging a person's fitness to drive should be based on individual medical assessment, and not blanket bans."
Experts are warning there is a diabetes "timebomb". Two million have been diagnosed with the condition in the UK, but another million are believed to have the condition without knowing it.
There are two types of diabetes. Type 1 is a disease that destroys the cells in the pancreas that produce the hormone insulin, needed to control blood sugar levels.
People usually develop the condition as children or young adults.
Type 2, or non-insulin dependent diabetes, is the most common form of the disease. It usually occurs in people who are over the age of 45 and overweight.
People with this form of the condition do not make enough insulin, or are unable to make proper use of it.
Left untreated, diabetes can lead to complications, including blindness, strokes, heart disease and lower limb amputation.
The Five Live Report - Britain's Diabetes Time Bomb was broadcast during The Worricker Show on Sunday 5 March between 1100 and 1200 on BBC Radio Five Live.