Why Sugar Makes Us Sleepy (And Protein Wakes Us Up)

Log in

Subscribers, enter your e-mail address for full access to the Science News archives and digital editions.

Not a subscriber? Become one now.



We posed this question to the brain panel… Mike – It depends on the time course. I’d be surprised if somebody would drink a cup of coffee then immediately feels sleepy. But I think it’s perfectly reasonable to feel sleepy a little bit later on because, what’s happening when you drink coffee, is that caffeine blocks the action of a “tiredness transmitter” in the brain called adenosine. Adenosine progressively damps down brain activity as it accumulates during the day, contributing to sleepiness. When we go to sleep, the adenosine is flushed out from the brain again so that we feel rested and refreshed when we wake up. If you block the effect of adenosine with caffeine, then you will feel more awake. But, later on, when the coffee effect wears off after it gets eliminated, which takes 4 hours or so, the adenosine is still there, and then that may kick in and make you feel sleepy. But I don’t know of a circumstances where you would drink coffee and then suddenly feel sleepy. Bill – Except, perhaps, if you had a strong association with coffee as a thing that you took next to going to sleep. Like children hear nursery melodies and they’re put to sleep by it. If you had a routine in which you drank coffee and then went to sleep, it may be a signal to sleep and would help you get to sleep. Is that possible? Hannah – Or maybe he associates coffee with incredibly boring activities like being in the office? Katie – Feeling really tired?

It’s the Sweetener, Not the Coffee

If you drink coffee sweetened with whipped cream, honey, syrup, or plain old sugar, you might feel tired if a sugar crash hits you.

When your body ingests more sugar than it’s used to, insulin is produced to offset it. However, the insulin also causes your blood glucose Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source levels to drop—and your blood glucose, also known as your blood sugar, is your body’s main source of energy.

So as your blood glucose levels decrease, you feel a lack of energy that can tire you out. You may also feel hungry, irritable, anxious, sweaty, dizzy, or on edge as the sugar crash hits.

It may not just be the sugar in your coffee, either. If you have a sweet snack such as a cookie or drink your morning coffee with a glass of orange juice (which can have as much sugar as five or six oranges), you might feel a sugar rush and subsequent decline. It’s particularly easy to binge sugary drinks, as they don’t fill you up the way food does.

If you experience a sugar crash, try having some protein to balance out your blood sugar levels.


Does low blood sugar cause fatigue?

Low blood sugar can also cause fatigue because your body is working harder to stabilize your glucose levels. Fatigue caused by low blood sugar is commonly experienced by those diagnosed with diabetes. Along with fatigue, individuals with diabetes may also suffer additional symptoms including; frequent urination, excessive thirst, extreme hunger, unexplained weight loss, and blurred vision. Though all of these symptoms account for fatigue directly, many of them may contribute to an overall feeling of sleepiness.

How do you know if your blood sugar is too high?

More often than not, most individuals do not even know they have high blood sugar. This is because high blood sugar usually doesn’t have any symptoms unless it is severe. In serious cases, you may experience nausea, shortness of breath, rapid heartbeat, and dizziness. If you are experiencing any of these symptoms, it’s best to contact your doctor for further recommendations. Other ways you can keep an eye on your blood sugar include using a blood sugar monitor at home or getting check-ups regularly with a physician.

Does consuming sugar cause you to snore?

Eating sugar can increase the natural production of phlegm and restricts your passages, causing you to snore. Furthermore, sugar increases the production of cytokines, a cell protein known to restrict airflow in your nasal passages. It’s best to avoid food with high amounts of sugar and try eating healthy dishes before bedtime to prevent snoring.

Will sugar keep me awake at night?

Eating too much sugar throughout the day can often lead to less restorative rest come nighttime. This is because sugar stimulates parts of your brain related to metabolism and appetite. Experiencing cravings at bedtime may cause late-night eating to disrupt your sleep. Additionally, research suggests individuals who consume large amounts of sugar often experience pain or stiffness caused by inflammation, making it harder to fall asleep.

How do I prevent my blood sugar from getting too high?

One of the best ways to keep your sugar at a healthy level is to eat balanced meals. Eating meals with high amounts of fiber helps slow down carb digestion and sugar absorption. This allows your body’s glucose to rise gradually rather than spiking to dangerous levels. It’s also best to drink plenty of water to prevent your body from becoming dehydrated. Drinking at least eight 8-ounce glasses of water has been proven to help your kidneys flush out the sugar in the body.

Can eating sugar before bed cause anxiety?

Consuming high amounts of added sugar can contribute to overall anxiety. When you eat sugary snacks in excess, your body’s blood sugar may rise and drop suddenly. These inconsistent glucose levels make it difficult for your body’s blood sugar to stabilize. As your body works to get your blood sugar back to normal, you may experience extreme fatigue or have feelings of worry, irritability, and general sadness.

Did We Help?

Coffee contains stimulating caffeine, but it has its limits. You might feel tired as you feel the effects of adenosine build-up, dehydration, decreased blood sugar, and more. The reasons you feel sleepy can vary, but the solution might be getting a better night’s sleep.

How Does Sugar Affects Sleep?

Sugar impacts sleep by affecting the hormone responsible for maintaining wakefulness. One of the hormones responsible for keeping you awake is Orexin. When the levels are low, you feel tired and sleepy. And when the levels increase, you become more active.

High consumption of sugar impacts sleeps by inhibiting the production of this hormone. Of course, that’s after you briefly feel energetic and alert. Hence, the more sugar you eat, the more you feel sleepy.

Orexin does control not only sleep but also controls hunger and some other metabolic processes in the blood. And that explains why people with chronically low levels of Orexin often suffer from narcolepsy or obesity. Apparently, what you consider as an energy boost actually lowers your orexin levels, which can be detrimental to your overall wellbeing. Interestingly, eating a large amount of sugar before bed can ruin your sleep, sometimes affecting how long it takes to fall asleep. Well, if you have a hard time falling asleep, there are white-noise machines that can make you sleep very quickly.

Also, consuming sugary food can make you sleepless and restless, and it can give you a dry mouth at night. It pulls you out of REM sleep and makes you feel tired in the morning. Apart from sugar crashes making you feel sleepy, other symptoms come with it. The symptoms include weakness, fatigue, shakiness, nausea, irritability, or headaches. Sometimes, you get hungry and start craving foods that will shoot up your glucose level. And then, the whole process begins again. Some call the process Blood Sugar Roller Coaster. Quite an interesting phenomenon, you’d agree.

Blood Sugar Crash

Indulging in a sweet treat or even drinking a soda may cause your glucose levels to spike. Though our bodies need sugar, we need to consume it moderately to prevent serious health problems, such as heart disease, diabetes, and kidney disease. When we eat or drink excessive amounts of sugar, our bodies release more insulin to regulate your rising blood sugar. As a result of the extra insulin in the body, your blood sugar drops, and you begin to feel tired—this is known as hypoglycemia or a sugar crash.

In addition to low energy, blood sugar crashes can cause uncomfortable side effects such as hunger, anxiety, headaches, and difficulty concentrating. Common symptoms of blood sugar crash also include, frequent wakes-ups, irritability, or discomfort at bedtime.

The Bottom Line

Eating sugar reduces the activity of your orexin system which is partially responsible for regulating your sleep and wake cycles. It’s why foods such as cake or candy can reduce your alertness and cause you to feel groggy. To prevent this, keep your daily sugar intake within the recommended range. Also, try to avoid eating lots of sugary foods at once as it can lead to a surge in blood sugar levels that may result in hyperglycemia symptoms.


This article is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional advice or help and should not be relied on to make decisions of any kind. Any action you take upon the information presented in this article is strictly at your own risk and responsibility!