According to a study of diabetes patients, intense treatment to lower blood sugar could prove to be as harmful as allowing glucose levels to remain high.
In the study, Cardiff researchers analysed nearly 50,000 patients with type 2 diabetes and found the lowest glucose levels linked to a heightened risk of death.
They also highlighted significant differences in death rates between patients on insulin and those taking tablets.
However, experts said that there could be various explanations for such results.
Patients taking insulin-based treatments have been urged not to stop taking their medication as a result of the findings.
The researchers used data from GPs and identified 27,965 patients with type 2 diabetes whose treatment had been intensified to include two oral blood glucose lowering agents - metformin and sulphonylurea.
A further 20,005 patients who had been moved on to treatment which included insulin were added to the study.
It was found that patients whose HbA1c levels - the proportion of red blood cells with glucose attached to them - were around 7.5 percent, ran the lowest risk of dying from any cause.
For both groups this risk went up by more than half if levels dropped to 6.4 percent, the lowest levels recorded.
For those with the highest levels the risk of death increased by nearly 80 percent.
But the risks appeared to be particularly pronounced among those on the insulin-based regimen than those on the combined treatment.
Irrespective of whether their HbA1c levels were low or high, there were 2,834 deaths in the insulin-taking group between 1986 and 2008, nearly 50 percent more than in the combined group.
The authors acknowledged there could be various factors associated with this, such as these being older patients with more health problems, who perhaps had had diabetes for a longer period of time.
They also mentioned a possible link between use of insulin and cancer progression, which had been reported in a different study.
"Whether intensification of glucose control with insulin therapy alone further heightens risk of death in patients with diabetes needs further investigation and assessment of the overall risk balance," the BBC quoted lead author Dr Craig Currie as saying.
"Low and high mean HbA1c values were associated with increased all-cause mortality and cardiac events. If confirmed, diabetes guidelines might need revision to include a minimum HbA1c value," he added.
The study has been published in The Lancet.