Honestly, high blood sugar is a bit of a silent predator. You might feel fine one minute, then suddenly you're chugging water like you've been wandering the Sahara for a week. It's weird. It’s subtle. When we talk about what happens if your sugar is too high, most people think of a quick "sugar crash" after eating too many cupcakes. But the biological reality is way more intense and, frankly, a lot more damaging than just feeling a little sleepy on the couch.
Blood glucose—or sugar—is basically the gasoline for your cells. But when that gas overflows and stays in your pipes (your bloodstream) instead of getting into the engine, things start to corrode. Fast. This state is known as hyperglycemia. If you've ever wondered why your doctor gets so stressed about an A1C reading of 7% or 8%, it’s because of the sheer chaos high glucose wreaks on your internal plumbing.
The Immediate Chaos: Why You Feel Like Trash
When your blood sugar spikes, your kidneys become the MVP of your body, but not in a good way. They have to work overtime to filter out the excess glucose. This leads to the classic "polys"—polyuria (peeing a lot) and polydipsia (being thirsty enough to drink a lake).
It’s a cycle.
The sugar pulls water out of your tissues to dilute the blood, your kidneys flush it out, and you end up dehydrated. This is why your mouth feels like it’s full of cotton balls. You might also notice your vision getting a little blurry. No, you probably don't need new glasses today; the high sugar is actually pulling fluid out of the lenses of your eyes, changing their shape. It's wild how fast that happens.
Then there’s the fatigue. It’s a cruel irony: your blood is packed with energy (sugar), but your cells are starving because the insulin isn't moving that sugar where it needs to go. You’re like a car sitting at a gas station with a locked fuel cap. You’re surrounded by fuel, but you’re running on empty.
The DKA Danger Zone
If things get really out of hand, especially for Type 1 diabetics or some Type 2s under extreme stress, you hit Diabetic Ketoacidosis (DKA). This is a literal medical emergency. Without enough insulin to use sugar, your body starts burning fat for fuel at a frantic pace. This produces ketones, which are acidic.
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Your blood literally starts becoming more acidic.
If you notice a "fruity" smell on someone's breath—kinda like Juicy Fruit gum or nail polish remover—that’s the acetone being exhaled. It’s a massive red flag. Mayo Clinic and the ADA (American Diabetes Association) emphasize that DKA can lead to a coma or worse if not treated with IV fluids and insulin immediately. It’s not something you "wait out" with a glass of water.
What Happens If Your Sugar Is Too High for Months or Years
This is where the real "silent" damage happens. You might get used to feeling a bit tired or thirsty. You adapt. But your blood vessels don't.
Think of high blood sugar like pouring syrup through a delicate mesh strainer. Over time, that sticky, thick blood damages the lining of the smallest blood vessels in your body. We call this microvascular damage. It’s why diabetes is the leading cause of blindness (retinopathy) and kidney failure (nephropathy) in adults.
- Your Kidneys: These are basically bundles of tiny filters called nephrons. High sugar batters them. They start leaking protein into your urine—something they should never do. Eventually, they just give up.
- Your Nerves: This is the one that really scares people. Neuropathy. It usually starts in the toes. A tingle. A numb spot. Then, eventually, it can turn into burning pain or a total loss of sensation.
- The "Invisible" Damage: High sugar also messes with your large blood vessels (macrovascular). This is why the risk of heart attack or stroke skyrockets when your blood sugar isn't managed. It accelerates atherosclerosis—the hardening of the arteries.
Dr. Richard Bernstein, a pioneer in blood sugar management, has often noted that the "normal" ranges set by some labs are actually still high enough to cause slow-rolling damage. He advocates for much tighter control to avoid these long-term "complications," which he argues aren't complications at all, but rather the predictable results of chronic hyperglycemia.
The Surprising Effect on Your Brain and Mood
We don't talk enough about the "sugar brain." High blood sugar causes inflammation in the brain. It’s been linked to "brain fog" and a higher risk of dementia later in life. Some researchers even call Alzheimer’s "Type 3 Diabetes" because of how closely related it is to insulin resistance and high glucose levels in the brain.
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Short term? You’re probably just irritable. Ever get "hangry" but in reverse? When your sugar is high, you might feel anxious, jittery, or just plain mean. It’s hard to be a pleasant person when your biochemistry is screaming at you.
Why Your Skin Breaks Down
Ever notice a dark, velvety patch of skin on the back of someone's neck or in their armpits? That’s called Acanthosis nigricans. It’s a huge billboard for insulin resistance and high blood sugar. Also, high sugar makes it way harder for your body to heal.
Bacteria love sugar.
If you have a cut on your foot and your blood sugar is 250 mg/dL, that wound is basically a buffet for infection. Combine that with poor circulation and nerve damage (so you don't even feel the cut), and you have the recipe for a foot ulcer that won't heal. This is the tragic path to amputation that affects thousands of people every year.
The Reality of "Spikes" vs. "Basal" Highs
It’s not just about your average. New research into "glucose variability" suggests that the "rollercoaster" effect—swinging from 80 to 200 and back—is actually more damaging to the blood vessel lining than a steady, slightly elevated level. These spikes create oxidative stress. It’s like hitting a wall at 60 mph versus scraping against it at 5 mph. Both are bad, but the sudden impact causes way more immediate structural failure.
Actionable Steps to Bring It Down Safely
If you’ve checked your sugar and it’s high, don't panic, but don't ignore it either.
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First: Hydrate. Drink water. Not Gatorade, not "sugar-free" juice. Just water. It helps your kidneys flush out the excess.
Second: Move. If you aren't in DKA (if you feel okay otherwise), a 20-minute walk can do wonders. Muscle contraction pulls glucose out of the blood without needing as much insulin. It’s like a cheat code for lowering your numbers. However, if your sugar is over 240 mg/dL and you have ketones, do not exercise. It can actually push your sugar higher.
Third: Review the "Why." Did you eat a massive bowl of pasta? Are you stressed? Are you getting sick? Illness is a huge trigger for high sugar because your body releases cortisol and adrenaline to fight the bug, and those hormones tell your liver to dump more sugar for "energy."
Fourth: Talk to your doc about your "Correction Factor." If you take insulin, you should know exactly how many points one unit will drop you. If you don't take insulin, you need to know at what point you should call the clinic or head to the ER. Most doctors say if you’re consistently over 300 mg/dL and can't get it down, it’s time for professional help.
Fifth: Long-term adjustments. High sugar is usually a sign that your current plan—whether it's diet, exercise, or meds—isn't keeping up with your body's needs. It might be time to look at a lower-carbohydrate approach or a change in medication like Metformin or a GLP-1 agonist, which have been game-changers for many people in stabilizing those daily numbers.
Managing blood sugar is a marathon. You’re going to have high days. Everyone does. The goal is to make those days the exception, not the rule, so your body doesn't have to pay the price years down the road.