Whether it’s from coffee, tea, soda, or chocolate, most people get caffeine every day. For healthy people, it’s usually a harmless perk-me-up. But if you have type 2 diabetes, caffeine may make it harder to keep your blood sugar in check.
One study looked at people with type 2 diabetes who took a 250-milligram caffeine pill at breakfast and another at lunchtime. That’s about the same amount as drinking two cups of coffee with each meal. The result: Their blood sugar was 8% higher than on days when they didn’t have caffeine. Their reading also jumped by more after each meal.
That’s because caffeine can affect how your body responds to insulin, the hormone that allows sugar to enter your cells and get changed into energy.
Caffeine may lower your insulin sensitivity. That means your cells don’t react to the hormone by as much as they once did. They don’t absorb as much sugar from your blood after you eat or drink. This causes your body to make more insulin, so you have higher levels after meals.
If you have type 2 diabetes, your body already doesn’t use insulin well. After meals, your blood sugar rises higher than normal. Caffeine may make it tougher to bring it down to a healthy point. This may lead to too-high blood sugar levels. Over time, this may raise your chance of diabetes complications, like nerve damage or heart disease.
Why Does Caffeine Have This Effect?
Scientists are still learning how caffeine affects your insulin and blood sugar levels. But they think it may work this way:
- Caffeine raises levels of certain stress hormones, like epinephrine (also called adrenaline). Epinephrine can prevent your cells from processing as much sugar. It may also keep your body from making as much insulin.
- It blocks a protein called adenosine. This molecule plays a big role in how much insulin your body makes. It also controls how your cells respond to it. Caffeine keeps adenosine from doing its job. It can’t clear sugar from your blood as quickly.
- It takes a toll on your sleep. Too much caffeine can keep you awake. Lack of sleep may also lower your insulin sensitivity.