If you’ve ever woken up in a pile of junk food wrappers—or just, you know, overdone it on Halloween candy in a less dramatic fashion—you may be familiar with the feeling of a sugar hangover. The unpleasantness you’re left with several hours after going all in on sweets (headache, fatigue, shakiness, general crappiness) can feel eerily like a booze-induced hangover. But what causes this cascade of awful symptoms? We spoke with a few experts to find out.
When you eat food, especially carbohydrates like sugar, your body acts quickly to keep your blood sugar at a normal level.
Unless you have a health condition like type 1 or type 2 diabetes, your body typically does a pretty great job of regulating your blood sugar, which is the concentration of glucose in your blood. Glucose serves as your body’s main source of energy, the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) explains, so keeping it in the right balance is important.
So, let’s say you eat some carbohydrates. In response, your pancreas secretes a hormone called insulin into your bloodstream to break down those carbs for energy, endocrinologist Clare Jung Eun Lee, M.D., an assistant professor of medicine at the Johns Hopkins University School of Medicine, tells SELF. This keeps the level of sugar in your blood within a normal range. (We’ll dive into how diabetes can influence this process in a bit.)
When the opposite problem occurs—your blood sugar drops due to too much energy expenditure (exercise) and/or not enough fuel (food)—your liver releases glucose it has stored for this very purpose, the Mayo Clinic explains. This helps maintain your blood sugar even when you’re running on fumes.
Consuming a high concentration of simple carbohydrates (like candy) can cause a more rapid and dramatic uptick in blood sugar than complex carbs (like brown rice).
“The extent to which your blood sugar is [changing] is different than if you were to have a well-balanced meal,” Dr. Lee explains. A well-balanced meal contains complex carbohydrates like whole-wheat products, which your body breaks down more gradually, as well as protein and fat to further slow that carbohydrate absorption.
Even if you devour a ton of simple sugars, your blood sugar should stay in a technically normal range because your pancreas will produce insulin to help convert it into energy. But, Dr. Lee explains, “You will still have a relatively large flux in your glucose.” Soon after eating a lot of sugar, you may feel an initial jolt of energy, especially if your blood sugar was on the low side before eating. After that, though, you may feel the start of that “sugar hangover” thanks to modest symptoms of high blood sugar, or hyperglycemia, such as fatigue, headache, and increased thirst, according to the Mayo Clinic. If you don’t have a condition like diabetes, the symptoms shouldn’t be severe and won’t be dangerous to your health. They just won’t feel great.
The “hangover” sensation really comes into play a few hours after you eat all that sugar, when the insulin your pancreas secreted after you ate causes a blood sugar dip.
While your pancreas usually gets it right, it can overcompensate. “Sometimes after a very high-sugar meal or beverage, an exaggerated amount of insulin is released to accommodate this sugar load,” Mary Vouyiouklis Kellis, M.D., an endocrinologist at Cleveland Clinic, tells SELF. Several hours later, as this insulin peaks, your blood glucose will start falling quickly. “You can get a ‘crash and burn’ effect,” Dr. Kellis says. “This phenomenon is known as reactive hypoglycemia.”
Again, your pancreas will keep your blood sugar within a technically normal range—this time by releasing a hormone called glucagon to keep your glucose up—but your blood sugar can still dip a little lower than you’re used to. When this happens, symptoms can include fatigue, headache, irritability, dizziness, confusion, blurry vision, shaking, sweating, and hunger, according to the Mayo Clinic.
To put it bluntly, this roller coaster that can come with eating a lot of sugar can make you feel like crap. Not only can you experience mild symptoms of low and high blood sugar, but the rapid fluctuation itself is something your body is probably not used to. “That large flux in your blood sugar and hormones is going to make you feel crummy,” Dr. Lee says.
The effects of sugar loading are more severe in people with type 1 and type 2 diabetes because their insulin responses don’t work properly.
“The fluctuation of the glucose is a lot more dramatic,” Dr. Lee says. “If you load a patient with diabetes with simple sugar, they won’t be able to keep their glucose in a normal range. It skyrockets.”
People with type 1 diabetes, a disease in which the pancreas does not make insulin (or makes very little), need to take insulin via injection or insulin pump, according to the Mayo Clinic. But if they don’t take enough insulin to cover the carbohydrates they consume, then their blood sugar can surge out of the normal range, Dr. Kellis says. This can even happen when the person takes the correct dose of insulin, Dr. Lee says. “Even if you did the best job and took the exact right amount, the insulin simply doesn’t work immediately—it takes a good 20 or 30 minutes,” she explains. “So, despite your best intentions to give the right amount of insulin on time, you might’ve already missed the boat.”
In type 2 diabetes, the form of the disease that’s more common in adults, people usually have insulin resistance, meaning the insulin is less effective, the Mayo Clinic explains. Their pancreas may not make enough insulin, either. In short, people with type 2 diabetes may not make sufficient insulin to handle a ton of sugar, Dr. Lee explains. To counter that, doctors typically recommend mostly eating foods that keep blood sugar as stable as possible (fruits, vegetables, whole grains), exercise to help control blood sugar, and possibly add insulin therapy, according to the Mayo Clinic.
When blood sugar soars outside the normal range, as it can in people with diabetes, it becomes much more serious than a sugar hangover.
The symptoms can become much more severe and include weakness, nausea, dehydration stomach pain, and vomiting, according to the Mayo Clinic. When you have high blood sugar for an extended period of time, your body starts to break down fat cells to use as fuel, producing a toxic buildup of acids called ketones in the bloodstream, Dr. Kellis says. Diabetic ketoacidosis can be life-threatening if not treated with insulin and fluids.
People with diabetes experience more extreme low blood sugar as well. For instance, people with type 1 diabetes can take too much insulin, causing their blood sugar to plummet. And they may not have the proper glucagon response from their pancreas to raise their glucose levels, Dr. Lee says, meaning they could fall into a life-threatening hypoglycemic coma if not treated immediately.
People with type 2 diabetes who take insulin may also administer too much, putting their blood sugar at a dangerously low level. Some people with type 2 diabetes take medications to increase their insulin sensitivity, which can trigger low blood sugar, Dr. Lee says. They typically have some glucagon injections to help bring their blood sugar back up, but if not administered quickly enough, this can also lead to a hypoglycemic coma.
None of the above is to say that you can’t enjoy sugar whether or not you have diabetes.
Steps like having some protein and fat with your sweets might help you evade a sugar hangover if you don’t have diabetes, so you can quite literally have your cake and eat it, too. If you do have diabetes and are planning on having more sugar than your body is accustomed to, be sure to follow your medication plan, including checking up on your blood sugar levels as often as prescribed. Better yet, if you know there’s, say, a certain sugar-themed holiday coming up and you want to partake safely, ask your doctor for guidance on how to do just that.