How to Tell When Your Sugar Is High: The Signs Your Body Is Sending You

You're sitting on the couch after a big meal, and suddenly, your brain feels like it’s been stuffed with cotton balls. You’re thirsty. Not just "I should grab a glass of water" thirsty, but a deep, unquenchable dryness that makes your tongue feel like sandpaper. Most people brush it off as being tired or having too much salt. But honestly, if this happens often, your body might be trying to scream at you about a spike. Learning how to tell when your sugar is high isn't just for people with a "diabetes" label on their medical chart; it's about understanding the internal chemistry that dictates your mood, energy, and long-term health.

Hyperglycemia—the medical term for high blood sugar—doesn't always feel like a sudden crash. Sometimes it’s a slow, creeping fog. It's subtle. Then it's not.

The Early Red Flags Most People Ignore

The first sign is usually the bathroom trips. If you find yourself waking up three times a night to pee, it isn't just "getting older." When there is too much glucose in your blood, your kidneys go into overdrive. They can't reabsorb all that sugar, so they pull fluids from your tissues to flush it out. This leads to the classic "polys" of diabetes: polyuria (excessive peeing) and polydipsia (excessive thirst).

It’s a vicious cycle. You drink because you're thirsty, then you pee because you drank, but the sugar is still pulling water out of your cells, so you’re still dehydrated. You might notice your skin feels unusually itchy or dry, or your mouth feels like it’s full of wool.

Then there’s the fatigue. This is the part that confuses people. "If I have high sugar, shouldn't I have more energy?" you might ask. Nope. Think of it like a gas station where the pumps are broken. The tanks (your bloodstream) are full of fuel (glucose), but the cars (your cells) can't get any of it. You’re literally starving in the midst of plenty. This leads to a heavy, lethargic feeling that no amount of coffee can fix.

Vision and Focus: The Blurry Reality

Have you ever noticed your vision getting a bit wonky after a high-carb meal? High blood glucose causes the lenses in your eyes to swell. This changes their shape and makes it harder to focus. It’s not permanent—usually—but it’s a massive indicator that your levels are out of whack. If you’re squinting at your phone more than usual, check your last meal.

Why Your Mood Swings When Your Sugar Soars

The brain is a glucose hog. It uses about 20% of the body's energy. When blood sugar levels are unstable, your brain is the first to complain. Irritability is a huge, underrated symptom of high blood sugar. You might feel "hangry" when sugar is low, but when it's high, many people report a specific kind of agitation or "brain fog."

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Dr. Anne Peters, a renowned endocrinologist at Keck Medicine of USC, often notes that patients feel "off" or "cloudy" when their levels exceed 180 or 200 mg/dL. You might find it hard to string sentences together or feel a weird sense of anxiety that has no external cause. It's basically a chemical imbalance playing tricks on your temperament.

The Weird Specifics: Breath and Digestion

Sometimes you can literally smell high blood sugar. When the body can't use glucose for fuel, it starts burning fat at a dangerous rate, producing ketones. This can make your breath smell fruity, like Pear drops or nail polish remover. If you smell that, it’s not a "cool quirk"—it’s a medical emergency called DKA (Diabetic Ketoacidosis).

You might also get hit with stomach pain or nausea. High sugar slows down "gastric emptying." Your stomach just sits there, full and heavy, leading to bloating or even vomiting. It’s a mess.

How to Tell When Your Sugar Is High Without a Meter

While a glucometer is the only way to be 100% sure, you can develop a "body literacy" to catch spikes early. Start paying attention to your "after-lunch slump."

• The 2-Hour Test: Notice how you feel exactly two hours after eating. If you feel a heavy pressure behind your eyes or a sudden need to nap, your sugar might be north of where it should be.
• The Ring Test: High sugar often causes mild inflammation and fluid retention. If your rings feel tighter an hour after eating a bowl of pasta, your body is struggling with the load.
• The Unexplained Headache: High glucose levels affect hormones that regulate vascular tone. A dull, throbbing headache that won't go away is a frequent companion to hyperglycemia.

Long-Term Consequences of "Living High"

If you ignore these signs, the damage becomes structural. We aren't just talking about feeling tired. Over time, high sugar acts like "shards of glass" in the bloodstream, damaging the delicate lining of your blood vessels.

According to the American Diabetes Association, chronic hyperglycemia leads to neuropathy—nerve damage. This usually starts in the feet. If you feel tingling, "pins and needles," or a strange numbness, your sugar has likely been high for a long time. The nerves are literally being starved of oxygen because the tiny vessels supplying them are damaged.

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Wounds also heal slower. If a small scratch on your leg takes three weeks to scab over, that’s a massive red flag. High sugar levels impair the immune system and prevent white blood cells from functioning correctly. Basically, your internal repair crew is on strike because the environment is too toxic.

Real Talk on Risk Factors

It's not just about what you eat. Stress is a massive, silent driver. When you’re stressed, your body pumps out cortisol and adrenaline. These hormones tell your liver to dump extra glucose into the blood to give you energy to "fight or flee." But if you’re just sitting at a desk stressed about an email, that sugar has nowhere to go. It just sits there, cooking your veins.

Actionable Steps to Manage a Spike

If you’ve realized your sugar is high, don't panic. Panic releases more stress hormones, which—you guessed it—raises sugar even more.

Hydrate like it's your job. Drink plain water. Avoid juices or sodas, even the "diet" ones, if you’re trying to flush your system. Water helps the kidneys filter out the excess glucose through urine. It’s the simplest, fastest way to start the downward trend.

Move your muscles. You don’t need to run a marathon. In fact, intense exercise can sometimes raise sugar temporarily. Instead, take a 15-minute brisk walk. Muscle contractions pull glucose out of the blood without needing as much insulin. It’s like opening a back door to let the sugar out.

Review your last meal. Was it all "naked" carbs? If you ate a bagel with nothing on it, that sugar hit your blood like a freight train. Next time, "clothe" your carbs with protein, fiber, and fat. Put avocado and an egg on that bagel. The fat and fiber slow down digestion, preventing the spike in the first place.

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Get a CGM if you can. Continuous Glucose Monitors (like the Dexcom or Libre) used to be only for Type 1 diabetics. Now, many people use them to see in real-time how a banana versus an apple affects them. It takes the guesswork out of how to tell when your sugar is high.

When to Seek Professional Help

If your sugar stays high despite drinking water and walking, or if you feel confused, short of breath, or start vomiting, go to the ER. These are signs of DKA, which can be fatal if not treated with IV fluids and insulin.

For everyday management, keep a log. Note when you feel that "brain fog" or "thirst." See if there's a pattern. Usually, there is. Most people find that high-stress Tuesdays or "Pasta Thursdays" are their danger zones. Once you see the pattern, you can break it.

Start by testing your fasting blood sugar in the morning. A normal reading is typically between 70 and 99 mg/dL. If you're consistently waking up over 100, it's time to have a real conversation with a doctor about insulin resistance or prediabetes. Catching it now is a lot easier than dealing with the complications five years down the road.

Keep a bottle of water nearby, watch for the "heavy eyes," and pay attention to how your body reacts to your plate. Your body is always talking; you just have to learn the language.