Initially, Savage had the diabetic lie on a biomat and gave him magnesium orally.
He then ransacked the diabetic's pantry, throwing out unhealthy foods and replenishing them with a selection of his own approved foods.
"The victim was somewhat reluctant to undertake the measure imposed on him by the defendant, but continued to do so for a period of time," the summary of facts states.
Savage stopped the diabetic's prescribed regular insulin injections because he believed they were no longer needed with his alternative treatment regime.
But the diabetic became increasingly ill without his insulin, "at this point, on two separate occasions, the defendant has inserted a needle into the victim's arm and administered an unknown liquid, intravenously".
The summary states the victim, in his ill state, was unable to stop Savage, and was worried about the effects of the medicine.
He described the needle being inserted into the vein as "very painful as the defendant pats his arm trying to find the vein".
When interviewed, Savage told police the diabetic was aware he did not have medical qualifications or New Zealand registrations and was a consenting patient.
On the second occasion of the intravaneous treatment, the diabetic was rushed to hospital after his son activated a medic alert device through St John.
Savage left Hawke's Bay soon after the diabetic's hospital admission and spent his time travelling throughout New Zealand.
In March, Hawke's Bay District Health Board issued a public warning urging people not to accept medical services, treatment or advice from Savage.
Earlier this month, it emerged that Savage had created a website, hosted in Iceland, which advertised biomats, touting them as a cure for cancer.
Cancer Society New Zealand had called his claims of curing cancer as "ludicrous".
Savage's defence counsel, Matthew Phelps, told Judge Adeane it was his client's first time before the courts and he had previously served for the Australian police force for 20 years. He began to explain his client's position, saying he had recently developed an interest in alternative medicine.
The judge interrupted, urging Mr Phelps to "save his powder" for sentencing.
Savage was arrested when he returned to New Zealand earlier this year, and on leaving again has no intention of returning, Mr Phelps said.
Medical Council of New Zealand website states doctors practising medicine here must be registered and hold a current practising certificate.
It is illegal to practise here without one. Savage will return to court on tomorrow for sentencing.