In people with diabetes there is not enough insulin released to moderate this peak in blood sugar and the damage it can do the body.
People at risk of type 2, known as adult onset diabetes, often have their blood sugar checked when they have been fasting.
But experts believe that testing the blood at this time rather than after a meal could mean that up to one-third of cases are being missed.
Coinciding with World Diabetes Day, the International Diabetes Federation has called for more widespread post-meal testing.
Dr Melanie Davies, consultant physician at Leicester Royal Infirmary, looked at glucose testing in a group of South Asian patients, who are at increased risk of developing diabetes.
Cases missed
Her team found that more than 30% of cases were missed because blood sugar readings were taken before food rather than two hours after eating.
Dr Davies also said that the accepted blood sugar level of between 6.1 and 6.9 should be lowered to 5.3 - 5.8 in order to detect all those with diabetes.
Dr Davies said this practice should be used not just for diagnosing diabetes but for ongoing monitoring.
"Seventy-five per cent of people with diabetes will die of heart disease and one of the puzzles we've had is why we've not been able to have any impact on that in the past ten to fifteen years," Dr Davies said.
"The problem is we've not been tackling it properly because we haven't been measuring the blood glucose properly."
Patients measuring their blood sugar before meals may believe they are doing reasonably well but it is the post-meal sugar level that will be the real predictor of any complications.
Research presented at the IDF's congress in Mexico earlier this month found that glucose levels measured two hours after eating are a better predictor of death than the fasting glucose level, so widely used.
The research, led by Dr Jaako Toumilehto, professor of public health at the University of Helsinki, looked at 256 deaths in diabetics.
Predictor of death
The two-hour blood glucose level significantly improved the ability to predict the risk of death.
Doctors believe the mealtime "spike" in sugar levels have a toxic effect and are a risk factor for heart disease and stroke.
The level of these spikes is detected by measuring the blood sugar after meals not before.
In people with diabetes there is not enough insulin released to moderate this peak in blood sugar and the damage it can do the body.
According to the IDF a consistently abnormally high blood sugar after food increases the risk of cardiovascular disease to the same level as a no-diabetic who has already had a heart attack.
Professor Sir George Alberti, president of the IDF, said that people should combine both the fasting glucose test and the post-meal measurement to ensure diabetes was properly detected and monitored.
"Half the problem is people are not being tested for diabetes at all so they don't know they've got it; the other half is not having the two-hour glucose level to show how likely they are to develop heart disease and stroke," he said.
Also coinciding with World Diabetes Day, the charity Diabetes UK has issued new guidelines on the standard of treatment patients should expect for their condition.
Diabetes UK says many of the 1.4 million people diagnosed with the condition in the UK are not getting the care they need.