An insulin pill made from a chemical found in shrimp shells is being developed by Taiwanese scientists.
People with diabetes must control their blood sugar levels
Researchers are looking for alternatives to the daily injections faced by people with diabetes.
The team from the National Tsing Hua University has found a "nanoparticle" shell that can protect the drug from being destroyed by stomach acid.
However, the doses currently needed to work in rat experiments far exceed those normally given to humans.
Insulin is needed by the body to stop the levels of sugar in the bloodstream getting too high.
People with diabetes cannot produce enough of this body chemical, and need to get more into their bloodstream.
Drugs which contain protein chemicals, including insulin, cannot survive exposure to stomach acid if swallowed, and the only viable alternative to injections is a nasal spray.
The Taiwanese researchers discovered a way to encase the drug in a shell which would resist stomach acid and other digestive fluids, and yet would be small enough to pass through the cells lining the small intestine and release their cargo into the bloodstream.
They put insulin into tiny spheres made of chitosan, a natural carbohydrate material derived from shrimp shells.
This was designed to be attracted to the intestinal lining, making it more likely that the spheres would be absorbed and deliver their contents in the right place.
The spheres were administered to laboratory rats given a drug to mimic the effects of diabetes, to see if this would bring down blood sugar levels in the animals.
While rats given plain insulin by mouth showed little or no change, those given the nanoshells loaded with the drug showed significant decreases, suggesting insulin was getting into their bloodstream.
The findings were reported in the journal Biomacromolecules.
However, a spokesman for Diabetes UK cautioned against people with diabetes expecting a pill to be available soon.
She said: "There are currently 700,000 people in the UK who take insulin injections, so being able to take insulin orally would have a great impact on their quality of life.
"At this stage the medication has only been tested on rats, at a time when they hadn't eaten for 12 hours.
"We would like to see further results of how the medication might affect people with diabetes who are eating a normal diet.
"Also, the research indicates that a large quantity of medication is needed in order to lower blood glucose levels.
"We would welcome further studies looking at making the medication more efficient and establishing its suitability for use in all insulin users."