Diabetics could one day take a pain-free insulin pill and need fewer injections, new research suggests.

Pre-clinical testing shows a newly designed type of oral capsule allows slow-acting insulin to be absorbed at a rate 50 per cent better than when it is injected.

The results mean diabetics could eventually swap out their slow-acting insulin injections for the capsules. However, most would still need to take injections for fast-acting insulin, given there was a lag with the capsule.

The capsule was designed by scientists in Melbourne, who say it tackles the long-standing issue of protein drugs degrading too quickly in the stomach.

"These types of drugs are typically administered with an injection," RMIT University biophysical chemist Professor Charlotte Conn said.

"Thousands of diabetics in Australia need insulin injections up to several times a day, which can be unpleasant for the patient and results in high health-care costs.

"The oral capsules could potentially be designed to allow dosing over specific time periods, similar to injection delivery."

The capsules still need further rigorous human trials, but they can also be used to orally deliver other protein drugs, including a new type of antibiotic that could avoid resistance by superbugs - also developed by RMIT researchers.

The capsule is designed not to break down in the stomach, with the insulin contained in a fatty nanomaterial that helps camouflage it so it can cross intestinal walls.

First author on the capsule study, Jamie Strachan, likened the technology to the Pfizer and Moderna COVID-19 vaccines.

"The mRNA in those vaccines is also packaged within fats, helping to keep the drugs active and safe during delivery in the body," he said.

The mRNA safely carries instructions for making a viral protein in the body, and activates people's immune systems.

RMIT has filed an international patent for the oral capsule technology.

The researchers' study was published in Biomaterials Advances.