It was the mangoes! What glucose trackers catch that lab tests miss

Continuous glucose monitors (CGMs) are revolutionising diabetes care by offering a real-time picture of how everything from your morning coffee to evening workout affects blood sugar levels. Pushpa Narayan speaks to Dr Vijay Viswanathan, president of the Research Society for the Study of Diabetes in India (RSSDI), about how these wearables are helping in diabetes management. Take a look...

How good are CGMs at monitoring blood sugar levels?

These wearables give real-time information about glucose levels, providing greater insight into the body’s sugar trends than traditional finger-prick tests. CGMs can show how different foods, exercise, sleep, and stress impact a person’s glucose levels 24x7. This data helps doctors offer dietary and medicinal adjustments to optimise blood sugar levels. Some studies suggest CGMs can detect early signs of impaired glucose tolerance or prediabetes even in those with normal HbA1c (2-3 month blood sugar average) levels. Also, the feedback can motivate people with diabetes to adopt healthier lifestyle choices such as regular physical activity and balanced diet.

When do you recommend them?

In specific cases. Last week, I had a patient whose HbA1c was 6.1, which is very good control for a person with diabetes, but the fasting and postprandial (after a meal) sugar levels were extremely high. We found it was possibly because my patient had been eating mangoes almost every day. HbA1c is the gold standard but doesn’t reveal glucose fluctuations that occur throughout the day. A normal HbA1c with frequent low and high blood sugar indicates wide swings that the average doesn’t capture. A high HbA1c despite ‘good’ clinic readings could mean post-meal spikes or overnight high sugar that are not being captured by intermittent testing. We recommend a CGM when a patient’s average might be masking significant glycemic variability. It provides the timing, magnitude, and frequency of fluctuations, allowing doctors to pinpoint the root cause of disparity and adjust meal plans and medical treatment accordingly.

Are they tools to improve diagnosis?

Yes. For instance, the Somogyi phenomenon or rebound hyperglycemia (high blood sugar) and the Dawn phenomenon are two distinct causes of high morning blood sugar in people with diabetes. Somogyi phenomenon occurs when an episode of low blood sugar (hypoglycemia) during the night triggers the release of counter-regulatory hormones such as glucagon, cortisol, and epinephrine which work to raise blood sugar. In diabetics who lack sufficient insulin, this mechanism can overshoot, leading to high blood sugar levels in the morning. Dawn phenomenon is a more natural process where the hormones cause a blood sugar rise between 2am and 8am to prepare for waking. These hormones increase insulin resistance and signal the liver to produce more glucose. In those without diabetes, the pancreas releases enough insulin but not in diabetics, leading to elevated blood sugar levels upon waking. Unlike Somogyi phenomenon, Dawn phenomenon is not preceded by a hypoglycemic event. It’s important to distinguish between the two as treatment varies. CGMs help the caregiver diagnose, adjust insulin dosage and medication timing, with better long-term health outcomes and lower risk of complications.

Even healthy people are using CGMs as a predictive health tool to prevent diabetes. Would you recommend it?

Doctors’ bodies, including RSSDI, are cautious about recommending widespread use in healthy people as the need is not yet proven. Also, most devices have algorithms tailored only to a diabetic’s needs, which can lead to data misinterpretation. There’s also the danger of an information overload that can cause anxiety, unwarranted dietary restrictions, and sometimes an unhealthy obsession with eating among healthy folk. Not to mention the needless spending. That said, manufacturers have designed over-the-counter devices for those who don’t use insulin and are not at severe risk of low blood sugar. For healthy people, I would recommend a balanced diet, exercise, and maintaining a healthy weight for glucose management.

Can CGMs help kids and the elderly?

They greatly reduce the need for painful finger-prick tests that kids may dislike and the elderly may have difficulty with. Both may be more susceptible to hypoglycemia and may not experience typical symptoms. A CGM can provide life-saving alerts for low glucose that would help prevent severe episodes. And modern CGMs are often user-friendly, which can benefit older adults with cognitive impairments.