Why does my blood sugar spike just before I wake up?

March 3, 2021

If you wear a blood sugar monitor as part of your ZOE test, sometimes you might notice changes in your blood sugar that you don’t expect. 

Earlier this month, one of our early customers reached out to ask us: “I noticed that my blood sugar spiked just before I woke up. Why did this happen?”

We talked to our blood sugar expert, Professor Paul Franks from Lund University, about the connection between your metabolism and your body clock and find out why some people might notice changes in blood sugar that aren’t caused by eating. 

The connection between your body clock and blood sugar

  • Your body uses your internal rhythms and biological feedback loops to keep your blood sugar in a healthy range throughout the day
  • At night your blood sugar stays within a fairly narrow range despite you not eating because your body releases stored glucose into your bloodstream (blood sugar) and makes glucose from other molecules
  • In the morning, your body begins to produce more glucose as it gets ready for the day, and insulin is released to avoid a morning spike
  • Join the ZOE program to gain insights into your blood sugar responses and get personalized recommendations tailored to your unique biology

Your blood sugar and your body clock are linked

Your body tries to maintain blood sugar levels as constant as possible throughout the day. It aims to keep your blood sugar high enough to supply your cells with energy, but not so high that you experience the harmful health effects that can come with prolonged elevated levels of sugar in your blood.

Our research has shown that the time of day can influence your blood sugar levels after eating. 

What’s more, studies have shown that insulin is secreted according to a daily (circadian) rhythm, with the highest levels between 12 pm and 6 pm and the lowest between 12 am and 6 am. 

So your blood sugar is intrinsically linked to your internal body clock and can fluctuate throughout the day, regardless of the food you eat.

How does your body manage blood sugar at night?

“Your body uses different types of energy in different ways at different times of day,” says Paul.

At night, your body uses less glucose because you are inactive. Instead, it burns more fat for energy, but it still needs glucose for vital bodily functions.

“Your brain relies almost exclusively on glucose for energy and still needs plenty of it even when you’re asleep,” explains Paul. “So it’s very important to have a constant supply of glucose overnight.” 

To ensure this happens, the body uses various biological feedback mechanisms, including hormones like insulin, which encourage your cells to remove sugar from your blood after you eat. 

There is also glucagon, which tells your liver to produce more glucose from fat and other sources if your blood sugar is dipping. 

Why might your blood sugar increase in the morning?

“Your body relies more on fat burning overnight but in the morning you have a preemptive shift back towards glucose, which can cause variations in blood sugar,” explains Paul. 

As your body prepares for the day, it increases the amount of glucose it makes, triggering an increase in insulin levels in order to keep your blood sugar levels stable as your metabolism powers up.

However, if you are insulin resistant or have diabetes, your body may not respond adequately to this insulin in your blood, resulting in increased blood sugar levels before you wake. This is known as the ‘dawn effect’ and tends to only be seen in people with diabetes. 

In people with diabetes who rely on insulin, morning blood sugar spikes can also be caused by taking too much or too little insulin before bed, resulting in a rebound effect in the morning. This is called the Somogyi phenomenon

I saw a rise in my blood sugar in the morning - does that mean I’m diabetic?

If you’ve been looking at your CGM data from your ZOE test, Paul cautions against over-analyzing every little bump and blip.

“We shouldn't interpret every bit of data that we see as being significant,” says Paul. “It's not just about your biology - it’s also about the technologies that we use to measure blood sugar, which aren’t perfect and can have some variability.”

So if you see a small rise in blood sugar in the morning, or a single larger blip, but have good blood sugar control throughout the day, you probably have nothing to worry about.

“Biological feedback from devices like CGMs is very powerful, but it can also be a source of anxiety,” says Paul. 
“It’s understandable that people who see spikes on their CGM might be worried about having pre-diabetes or diabetes. But we must balance the probabilities and ask, is it a one-time thing? Is it real? Is there a pattern? If there is a pattern, that’s when you might want to be concerned and seek out a medical opinion, but if not, it is probably not worth worrying about.”

If you’re worried about your blood sugar levels or are experiencing any symptoms of prediabetes - such as being unusually thirsty or hungry, peeing more often, feeling abnormally tired (fatigue), or blurred vision - you should see your doctor.

ZOE can help you understand your blood sugar responses, and much more

Our at-home test allows you to gain deep insights into how your body responds to food. Not only do we measure how your blood sugar levels change after eating, but we also monitor changes in fat responses and inflammation, as well as analyzing the unique mix of “good” and “bad” microbes in your gut

We then use this information to give you personalized food recommendations tailored to your unique biology, so you can be empowered to reach your health goals.

Join ZOE today to learn how to eat for your body, for life.

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