Are Blood Sugar Spikes Really That Dangerous?
In recent years, two surprising trends have emerged. Healthy people have started wearing continuous glucose monitors (CGMs) to track their blood sugar throughout the day, while others have cut out refined carbohydrates like white bread and pasta entirely. Some wellness influencers even claim that blood sugar spikes—even in people without metabolic disease—can lead to hormonal imbalances, acne, mood swings, and worse.
But experts are pushing back. Here's when to worry, and when a carbohydrate-heavy meal is unlikely to do any lasting damage.
Why Does Blood Sugar Spike?
When we eat and digest sugary foods—such as refined sugar, fruit, and carbohydrate-rich foods—our blood sugar naturally rises. As carbohydrates and sugars are broken down into glucose, it is absorbed into the bloodstream, temporarily raising blood sugar levels. The pancreas responds by secreting insulin, which helps move glucose out of the bloodstream and into cells for energy.
Food isn't the only trigger. During high-intensity exercise, hormones like adrenaline signal the liver to release more glucose into the bloodstream, providing extra fuel for working muscles. As a result, blood glucose can temporarily rise, says Jennifer Sherr, a paediatric endocrinologist at Yale School of Medicine in Connecticut, US.
In people with diabetes, the body doesn't produce enough insulin, or it no longer works properly (insulin resistance). This means that after eating, their blood sugar can become dangerously high. For them, carefully managing diet, exercise, and blood sugar levels is essential. Some also need medications such as insulin or metformin.
Glucose Spikes Are Normal in Healthy People
Among healthy individuals, a rise in blood glucose after eating is a normal physiological response. "The biggest misconception is that every glucose spike is harmful," says Adrian Brown, associate professor in nutrition and dietetics at University College London, UK.
Blood sugar typically peaks around one hour after eating and returns to baseline within the next two hours. If a spike is brief and occurs in someone with normal metabolism, we should not be concerned, says Brown.
It's when blood glucose remains elevated for longer than expected that it could indicate the body is not regulating glucose normally, says Sherr. This could be a sign of insulin resistance, which can develop after long-term exposure to high blood sugar levels. Eventually, it can lead to prediabetes and type 2 diabetes. Persistently high blood glucose in diabetics can lead to complications including nerve and eye damage, heart disease, and stroke.
However, some experts argue there isn't enough evidence to say that excessive blood glucose directly causes insulin resistance. Instead, when we eat more than our body needs, excess calories tend to be converted to fat, says Nicola Guess, a dietitian and senior research fellow at the University of Oxford, UK. The resulting weight gain is a risk factor for type 2 diabetes, she adds.
The Rise of Continuous Glucose Monitors
People with diabetes already monitor their blood sugar regularly, often using continuous glucose monitors (CGMs) that measure levels throughout the day. There's now a growing commercial market for these devices among otherwise healthy people. However, some experts warn they are unnecessary for those without diabetes. One study of non-diabetic participants found their blood sugar levels were in the healthy range 96% of the time.
Others caution that CGMs can "prompt harmful dietary changes and distort perception of health," especially as they can overestimate blood sugar levels. In a recent review, Brown and colleagues found "a lack of consistent, high-quality evidence showing that CGMs improve health outcomes in people who do not have diabetes."
The exception may be those at risk of type 2 diabetes. Emerging research suggests that trackers monitoring blood glucose could help predict those at greater risk, says Sherr, but more evidence is needed to determine if CGMs are beneficial to this group.
A Balanced Diet Is Still Best
While blood sugar rises are normal and unlikely to lead to dire consequences in healthy people, there are some benefits to helping your body keep sugar levels steadier. For example, a rapid post-meal glucose dip can increase hunger and lead to greater energy intake overall.
Different types of meals also affect how much our blood sugar changes. Foods that keep blood sugar steady—such as wholegrains and protein-based foods—can keep us fuller for longer. Simple carbohydrates like white bread and white rice are absorbed into the bloodstream more quickly.
The order in which you eat certain foods can also help. For instance, eating protein and vegetables before carbohydrates has been found to reduce the subsequent rise in blood sugar that normally follows a carbohydrate-rich meal.
Another tip is to aim for balanced meals containing protein, fibre-rich plant foods, and healthy fats. This can help slow digestion, provide a steadier supply of energy, and help maintain a healthy weight.
It's also worth noting that we all respond slightly differently to the food we eat. "There is considerable variation between individuals, and the same person may show different responses depending on factors such as sleep, stress, activity levels, and the type of meal consumed," says Brown.
In addition, avoiding carbohydrates—as certain diets suggest—could backfire, says Guess. When we eat a carbohydrate-rich meal after a period of restriction, it can actually cause our blood sugar to rise more than usual. Crucially, carbohydrates are considered an essential part of a balanced diet. As Guess notes in a recent review, restricting certain food groups can mean unnecessarily avoiding foods that are good for you.
So while the jury might be out on the benefits of glucose monitoring, in the meantime, it helps to remember that the majority of us already eat too much added sugar. We can certainly work on reducing that instead.
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