What Happens to Your Brain + Body During a Low?

If you live with diabetes and take insulin you’ve probably experienced low blood sugar. Low blood sugar (aka hypoglycemia) is most common in people with type 1 diabetes (T1D).

But do you know what actually happens to your body when you’re going through a low? In this guide, we break down the science.

What causes low blood sugar and how does it feel?

First, let’s break down why low blood sugar happens in the first place and how it feels and shows up to others. Low blood sugar happens any time your blood sugar levels drop below 70 mg/dL (3.9 mmol/L). Severe low blood sugars start at 55 mg/dL (3.1 mmol/L). 

Low symptoms can include:

• Shakiness
• Dizziness
• Lack or loss of balance
• Sweating, chills, clamminess
• Confusion
• Irritability, being nervous, anxious 
• Feeling sleepy or weak 
• Hunger
• Rapid heartbeat
• Color draining from skin (pallor) 

Severe low symptoms can include:

• Loss of consciousness 
• Seizures 

Why do low blood sugars happen?

Low blood sugar can occur for a variety of reasons. Some of the most common examples include:

• You dosed your insulin regularly for a meal, but didn’t account for the exercise you’d get later.
• You miscalculated an insulin dose for a tricky or unknown food. Maybe you thought it had more carbohydrates than it actually did or didn’t account for how its carbs, fats and proteins would interact with your blood sugar levels.
• You took small doses back to back in a short period of time (aka stacked your insulin).
• You couldn’t wait for your high blood sugar to come down, so you rage-bolused and got a rebound low.
• You have too much basal (background) insulin in your system.
• You drank alcohol before bed and have rebound low blood sugar.
• You were physically active too close to bedtime and have rebound blood sugar.

In most cases having a low blood sugar is not your fault and they’re nothing to feel ashamed about. It is important, though, that they are addressed quickly. If not, low blood sugar can become extremely dangerous and require  emergency glucagon.

What happens to your body during a low

So, now that you know why they happen and how they feel, let’s jump into what actually happens to your body during a low. If you follow diabetes content creators on Instagram or TikTok, you might’ve seen some of the viral videos that say things along the lines of “we’re actively trying not to die every day.” 

And, honestly—while that sounds dramatic—it’s not too far off. 

Living in a body with diabetes means balancing a lot—24/7 blood sugar monitoring, carb counting for every meal and snack, having to plan for exercise or movement, navigating insurance, constant trips to your pharmacy…the list goes on!

There are no breaks in life with diabetes, and low blood sugars especially demand immediate attention. When your body experiences low blood sugar, it’s actively shutting down. This is because your brain relies on glucose (sugar) to function. 

Simply put, low blood sugar occurs when you have too much insulin and not enough sugar flowing through your body.

Harvard Medical School explains that if your blood sugar is below 70 mg/dL (3.9 mmol/L), your nervous system is also starved of fuel. This triggers distress signals to your brain. If your brain doesn’t have enough sugar, it also doesn’t get enough oxygen. The Centers for Disease Control (CDC) describes the brain as the body’s command center, and when it experiences low blood sugar, the command center takes a hit and goes off balance. 

When your command center is off balance, your whole body can go off balance in a hurry. That’s a low!

Why does your body shut down during a low?

When your brain doesn’t have enough sugar, iIt can’t function because sugar is the fuel it runs on. 

If your low blood sugar is severe, your body may experience:

• Brain shutdown: When your blood sugar drops below 55 mg/dL (3.1 mmol/L), your brain can start to have serious problems. If you don’t notice your blood sugar is low (because you have hypoglycemia [hypo] unawareness), you might not even realize it’s happening. But even if you don’t realize it, your brain is still suffering. When your brain doesn’t get enough sugar, you might see things that aren’t there (hallucinations) or act unlike yourself.
• Loss of consciousness: Because of the crazy energy drain your body is going through during a low, you might lose consciousness if your blood sugar is severely low.
• Seizures: When your body goes through a severe low, it can also cause convulsions because the neurons in your brain are firing incorrectly.

Remember, the shutdown is due to the lack of fuel (sugar) to the brain.

How do repeated low blood sugars affect your body?

Over an extended period of time, frequent low blood sugars can cause other issues like:

• Permanent brain damage: Long-term, untreated or mismanaged low blood sugars can result in permanent brain damage for some people with diabetes (PWD). It’s rare, but it happens.
• Cardiovascular problems: Low blood sugar doesn’t just affect your brain. Your heart also needs a steady supply of sugar. If your blood sugar drops often, you might notice changes in your heart rate, rhythm or blood pressure over time.
• Depression: Dr. Gregory Jantz, The Center, a Place for Hope—a top 10 facility for the treatment of depression—explains that low blood sugar can mimic depression or make it worse. When blood sugar is low, it can stop the body from making important chemicals called neurotransmitters, like serotonin, which makes you feel happy. This can cause feelings of sadness, increased worry or trouble dealing with stress.
• Self-esteem and decision-making skills: Jantz also says that chronic low blood sugar can affect how someone makes decisions. It can affect how a person with diabetes feels about themselves, whether they feel they belong or how confident they are.

Chronic low blood sugars can also cause:

• Moodiness
• Irritability
• Lack of energy and chronic fatigue 
• Feeling like you’re not enough

All because of sugar

“At least it’s not emergency broccoli,” is what many diabetes content creators chalk up low blood sugar treatments to, but the seriousness of these events shouldn’t be underestimated. Severe lows send your body into a tailspin, and chronic lows can have long-term consequences.

Living in a body with diabetes is undoubtedly a balancing act. Sugar can be tasty and heroic when it comes to lows, but it can turn into a villain quickly when there is too much or too little flowing through your bloodstream. Finding the best fast-acting carbohydrates that work for your body is key.

The future of automated glucose delivery to get ahead of lows

Thankfully, technology, medication, support and education have improved for many PWD over time. Looking to the future, diabetes technology manufacturers are exploring ways to integrate glucose delivery into smart systems.

The future isn’t here yet, but in the present, you can still get ahead of lows to prevent their impact on your system. Your body deserves attention and care.

Are you feeling a bit unsure about managing diabetes or in need of a refresh? Use our Beyond Diagnosis guides to regain confidence and begin nurturing your body better with diabetes.