Dr Sarah Brewer said: “The main reason why everyone experiences a slightly a higher blood sugar level in the morning is known as the dawn phenomenon.”
She explained: “For people without diabetes, the rise in glucose is minimal, but for those with diabetes, blood glucose levels stay higher than normal.
“One study found that around 55 percent of people with diabetes experienced the dawn affect, but others have not found the same prevalence.
“The dawn phenomenon is due to our natural biorhythms in which production of insulin hormone (which lowers glucose) is suppressed during sleep, and levels of other hormones that raise glucose (growth hormone, glucagon and cortisol) increase.
“There is also a theory (known as the Somogyi effect) which suggests that, in people with diabetes who are on insulin, the rise in blood sugar in the morning could be a rebound effect of using too much or, conversely, too little insulin the evening before, but this is controversial.”