ANCHOR: PETER MANSBRIDGE

PETER MANSBRIDGE: Ever since it was discovered eighty years ago, insulin has been a life saver for diabetics around the globe. But now there's a controversy surrounding the critical drug. Its makers have changed the way they manufacture it, and some diabetics say the newer formula is causing them serious health problems. Erica Johnson of the CBC program Marketplace has been investigating this story.

UNIDENTIFIED WOMAN (1): Okay, Brook, let's go.

ERICA JOHNSON (Reporter): Colleen Fuller has been a diabetic since she was sixteen. She used animal insulin made from cows and pigs, and managed her disease well. But six years ago, her doctor urged her to try a newer, genetically engineered, or synthetic insulin called Humulin.

COLLEEN FULLER (Diabetic): The first night that he put me on Humulin, I went into a coma. My husband had to phone 911. And that happened about four more times over the next month and a half. It was very awful.

JOHNSON: Fuller isn't alone. Since 1998, Health Canada has heard from one hundred and twenty-one patients and doctors who say synthetic insulins have caused problems - comas, seizures, convulsions, hypoglycaemia, a sudden drop in blood sugar levels that can cause a person to black out. South of the border, the US Food and Drug Administration has received thousands of similar reports. Some doctors and patients believe Humulin has caused disorientation, sent people to hospital. It even leads to death. No one from the drug company Eli-Lilly would appear on camera, but a spokesperson insisted everyone can handle the drug.

DR. LOREN GROSSMAN (Eli Lilly Canada): When they switch from animal to human insulin, with proper assistance, they can do so safely and efficaciously.

JOHNSON: For the vast majority of diabetics, synthetic insulin works well. Thousands are switching to it because most of the animal insulins they used to take have been phased out. The drug companies say, in the long-term, synthetic insulin will be cheaper to make, and it's closer to insulin actually produced by the human body, so that means just one animal insulin remains available in Canada, and it's hard to find.

UNIDENTIFIED MAN (1): That's just outrageous

JOHNSON: Fuller and other diabetics are angry their insulin choices are disappearing. They claim their health is suffering.

UNIDENTIFIED MAN (1): I get so low, that I'm not able to tell how low I am until I can't help myself.

JOHNSON: And, they say, Health Canada has a duty to keep animal insulins on the market. But Health Canada says it doesn't have enough evidence to be concerned, and it points out drug companies are entitled to stop making a product.

IAN MacKAY (Health Canada): We simply just don't have the authority to force the manufacturer to continue marketing something that they have chosen to withdraw from the market for their own corporate reasons.

JOHNSON: Right now, diabetics who need their old animal insulins have to import them from Britain, and most provinces won't pay for them. An outrageous situation, according to Fuller, who's starting a campaign to get the insulin she says she needs back on pharmacy shelves.

FULLER: I know it's going to be a long fight, and I'm ready.

JOHNSON: Erica Johnson, CBC News, Vancouver.

MANSBRIDGE: And you can watch Erica's full report tomorrow night on Marketplace at eight o'clock, eight thirty in Newfoundland.