You don’t need a degree in medicine to know the wonders a good night’s sleep can do. But as well as helping you start the day in a better mood, did you know that sleep can affect blood sugar levels, and by extension, type 2 diabetes? 

Our body’s ability to control blood sugar varies naturally throughout the day based on the rhythm of our metabolism. When our sleep is disrupted, it can throw this rhythm, and therefore our blood sugar levels, out of balance.[1]

For folks with type 2 diabetes, this means that a poor night’s sleep can affect how well their body can keep blood sugar levels in check the next day.[1]

An estimated 4.9 million people in the UK have diabetes,[2] and of these, over 90% have type 2.[3] All of these people need to sleep, so if you have type 2 diabetes, it’s important to understand the link between quality, consistent sleep, and blood sugar. Here’s everything you need to know.

Blood sugar and our body clock‍

Before we can understand the link between diabetes and sleep, we first need to talk about blood sugar. 

Our body naturally runs on a 24-hour cycle known as the circadian system, aka our body clock, that anticipates our routine and organises our metabolism to respond appropriately—like getting us ready to sleep at nighttime and processing food after meals.[4]

One of the processes influenced by our circadian rhythm is how well our body can turn glucose that we get from food and drink into energy.[4] The medical term for this is glucose tolerance, and a useful way to think of it is as an indicator of how well our body can control blood sugar.  

In a typical 24-hour cycle, glucose tolerance is at its lowest in the middle of the night, but peaks in time for breakfast, when we’d normally wake up.[5]  

When our regular cycle is disrupted, say from late or sleepless nights, this can throw our body’s rhythms out of balance—which then can mess with our glucose tolerance. 

Our body clock expects that we’ll be awake during the day, when it’s light, and asleep during the night when it’s dark. When we’re awake at night, this causes what’s called a “circadian misalignment”, and this is associated with lower glucose tolerance.[6] It’s for this reason that night shift work is considered a risk factor for diabetes.[7]

For people with type 2 diabetes, this means that sleep plays a role in controlling their blood glucose levels, including preventing blood sugar spikes when they wake up the next morning.[1]

Sleep and blood sugar ‍

Researchers are still looking into the connection between sleep and blood sugar, but we do have evidence that certain disruptions to sleep can affect our glucose tolerance. 

In one recent study of 953 people without any health conditions, those who had better quality sleep had better blood sugar control the next morning.[1] Better quality sleep is measured here as how long you spend in bed actually asleep, versus lying awake or tossing and turning.

Similarly, people who went to bed later were less able to control their blood sugar the next day—even if they slept in.[1] This aligns with what we know so far about our body clock: if you upset its routine, your metabolism will react.

People with type 2 diabetes who slept 6-8 hours per night had lower blood sugar levels than those who under- or overslept

Lee et al., Sleep Med Rev

 How long we sleep for has also been linked to changes in blood sugar, however according to some studies, this doesn’t play a major role in defining glucose tolerance.[1]

More research is needed to know for sure, but there does appear to be a link between the two: in one 2017 review of 20 studies, people with type 2 who regularly slept less than 6 hours or overslept (between 8-9 hours) were found to have higher blood sugar levels than those who slept 6-8 hours per night.[8]

Not having deep sleep, which is sometimes called slow-wave sleep, has also been shown to reduce glucose tolerance—this may be because it puts the body in a state of stress, which then increases insulin resistance.[9]

Type 2 diabetes and sleep‍

We know that there’s a link between sleep and blood sugar, but it also works the other way around: blood sugar and diabetes in particular can also influence sleep. 

High blood sugar levels have been associated with poor quality of sleep,[10] and can also cause diabetes symptoms that make it harder to get to sleep, like needing to pee more frequently or feeling thirsty. Type 2 diabetes is also linked to a number of sleep disorders, including insomnia[10] and obstructive sleep apnea.[11]

High blood sugar levels have been associated with poor quality of sleep

Tsereteli et al., Diabetologia

This isn’t to say that everyone with type 2 diabetes is going to have terrible sleep, only that there are links between the two that it’s important to be aware of. 

Plus, in itself, poor sleep is considered a risk factor for type 2 diabetes. Studies have shown that people who sleep between 5-6 hours a night are twice as likely to be diagnosed with type 2, while those who oversleep are 60% more likely to develop the condition compared to those who get 7-8 hours a night.[12] 

Can better sleep help with my diabetes? ‍

While we’re learning more about the role sleep plays in our overall health, there’s still plenty we don’t know—including whether sleep could be used as part of diabetes treatment. 

As it stands, we don’t have enough evidence to say for sure that a good night’s sleep can help treat or improve type 2 diabetes, nor the extent to which it could do so. 

But the science does show that a good night’s sleep can improve blood sugar control and that sleep, in general, is fundamental to keeping our metabolism in balance.[1] In other words: a good night’s sleep is always going to do you good. 

Lifestyle is a crucial element of type 2 diabetes treatment, and alongside diet and exercise, sleep is an important part of a balanced and healthy routine. Sleep isn’t a substitute for any medication your doctor prescribes nor making sure you eat well, but it certainly helps your body to operate at its best.

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