High blood sugar can quietly affect your body for years before you ever hear the word “diabetes” in a doctor’s office. You may feel “off” or more tired than usual, but nothing that seems urgent enough to call your doctor about. The truth: those small changes can be your body’s early alert system.

In this guide, we’ll walk through 11 evidence-based symptoms of high blood sugar that doctors say you shouldn’t ignore—whether or not you’ve been diagnosed with diabetes. You’ll learn what’s happening in your body, how serious each sign might be, and practical steps you can take today.

This article is for educational purposes and isn’t a substitute for medical care. If you recognize yourself in several of these symptoms, it’s worth reaching out to a healthcare professional for testing and a personalized plan.

Woman checking blood sugar level at home with a glucose meter
Monitoring blood sugar regularly can help you catch changes before they become emergencies.

Why High Blood Sugar Symptoms Are Easy to Miss

High blood sugar (hyperglycemia) happens when there’s too much glucose circulating in your bloodstream and not enough insulin—or insulin isn’t working effectively—to move it into your cells. Over time, this can damage blood vessels and nerves, increasing the risk of heart disease, stroke, kidney disease, vision loss, and more.

The challenge is that these changes rarely happen overnight. Early symptoms are often subtle, come on gradually, and can easily be blamed on stress, aging, or “just being busy.” That’s why knowing the patterns doctors look for can make such a difference.

“People are often surprised to learn they’ve had elevated blood sugar for years. When we ask about symptoms, they realize their body had been whispering to them for a long time.”
— Endocrinologist, academic medical center (clinical observation summarized from recent reviews)

Let’s look at 11 of the most common symptoms of high blood sugar that deserve your attention.


1. Increased Thirst That Just Doesn’t Quit (Polydipsia)

Feeling thirsty after a workout or a salty meal is normal. But when your blood sugar runs high, you may feel thirsty all the time—even if you’re drinking plenty of water.

With high blood sugar, your kidneys try to flush out the excess glucose through urine. That fluid loss can quickly lead to dehydration, which triggers more thirst.

  • Needing to carry water everywhere and still feeling parched
  • Waking up at night with a dry mouth
  • Clear or light-colored urine but ongoing thirst

2. Frequent Urination, Especially at Night (Polyuria)

Having to pee more often can be one of the earliest and most common signs of high blood sugar. When glucose levels are high, your kidneys reach a “threshold” where they can’t reabsorb all the sugar. Glucose spills into the urine and pulls water with it, creating larger volumes of urine.

This can show up as:

  • Needing to urinate every 1–2 hours during the day
  • Waking up multiple times at night to pee (nocturia)
  • Accidental leakage in people who previously had good bladder control

Other conditions—like urinary tract infections, prostate problems, or certain medications—can also increase urination, so it’s important to get evaluated rather than self-diagnose.


3. Unusual Fatigue or “Energy Crashes”

Glucose is your body’s main fuel source. Ironically, when glucose is stuck in the bloodstream, your cells can’t use it efficiently—so you may feel drained, foggy, or like you’re dragging yourself through the day.

People with high blood sugar often describe:

  • Feeling exhausted after meals
  • Needing more naps or caffeine than usual
  • Physical tiredness plus mental “brain fog”
Tired person resting on a couch holding a mug, appearing fatigued
Persistent fatigue—especially after meals—can be an overlooked sign of poorly controlled blood sugar.

4. Blurry Vision That Comes and Goes

High blood sugar can change the shape and flexibility of the lens inside your eye by pulling fluid into and out of it. This can temporarily alter your focusing ability, leading to blurry vision.

  • Difficulty reading small print that used to be clear
  • Vision that seems to “sharpen” or “blur” as the day goes on
  • Needing frequent prescription changes at the eye doctor

Long-term, chronically high blood sugar can damage the tiny blood vessels in the retina, leading to diabetic retinopathy—a serious complication that can threaten vision. Regular dilated eye exams are essential for anyone at risk.


5. Slow-Healing Cuts, Scrapes, or Infections

High blood sugar impairs several parts of the immune system and reduces blood flow, particularly to the skin and extremities. That combination makes it harder for your body to fight infection and repair tissue.

You might notice:

  • Minor cuts or scratches taking weeks to heal
  • Frequent skin infections, such as boils or cellulitis
  • Recurring gum infections or periodontal disease
“In clinic, we often see people referred to us because of a stubborn foot ulcer or recurrent infections, and blood work reveals previously undiagnosed diabetes.”
— Summary of findings from primary care and endocrinology case reports

6. Tingling, Numbness, or Burning in Hands and Feet

Over time, high blood sugar can damage nerves—a condition called diabetic neuropathy. Early on, this often feels like tingling, “pins and needles,” burning, or numbness in the feet and sometimes the hands.

  • Sensations are often worse at night
  • You might feel like you’re “walking on cotton” or unable to feel small injuries
  • Some people notice increased sensitivity—light touch feels painful

Nerve damage is partly related to how high your blood sugar is and how long it’s been elevated. Earlier detection and better glucose control can help slow or sometimes partially reverse progression.


7. Unexplained Weight Loss (Often with Type 1 or Very High Glucose)

While many people associate high blood sugar with weight gain, significant unexplained weight loss can also be a warning sign—especially in type 1 diabetes or severe, untreated type 2 diabetes.

When your cells can’t use glucose for energy, your body starts breaking down fat and sometimes muscle for fuel. That can lead to:

  • Losing more than 5–10 pounds (2–4+ kg) over a few months without trying
  • Increased appetite but continued weight loss
  • Clothes feeling looser even though your habits haven’t changed

8. Increased Hunger and Cravings (Polyphagia)

High blood sugar doesn’t always mean you lose weight. Many people notice they’re hungrier than usual—particularly for carbohydrate-heavy foods—even though they’re eating regular meals.

Because glucose isn’t efficiently entering your cells, your brain gets the message that you’re still “low on fuel,” and ramps up hunger signals. You might experience:

  • Feeling hungry soon after eating
  • Strong cravings for sweets or refined carbs
  • Eating more than usual without feeling satisfied

9. Recurrent Yeast or Fungal Infections

Yeast and some fungi thrive in warm, moist, and sugary environments. Elevated blood glucose can increase sugar in body fluids, which can feed these organisms and make infections more likely.

Common patterns include:

  • Recurrent vaginal yeast infections
  • Jock itch, athlete’s foot, or under-breast rashes
  • Cracking, itchy skin between toes or in skin folds

10. Dark, Velvety Patches of Skin (Acanthosis Nigricans)

One visible sign that your body may be struggling with insulin resistance—a key driver of type 2 diabetes—is acanthosis nigricans: darkened, slightly thickened, velvety patches of skin.

These areas most often appear:

  • On the back of the neck
  • In armpits, groin, or under the breasts
  • On elbows, knuckles, or knees
Acanthosis nigricans can be an external clue to insulin resistance and higher risk for type 2 diabetes.

This condition can occur with other hormone disorders and some medications, so an evaluation by a healthcare professional or dermatologist is important.


11. Mood Changes, Irritability, or Brain Fog

Your brain is highly sensitive to changes in blood glucose. While we often talk about low blood sugar causing shakiness and irritability, swings into higher ranges can also affect mood and cognitive function.

  • Feeling unusually irritable or “on edge”
  • Difficulty focusing, slowed thinking, or forgetfulness
  • Headaches that seem tied to meals or sugary foods

Mental health conditions like anxiety and depression are common and multifactorial, but increasingly, research highlights a two-way relationship between metabolic health and mood. Addressing blood sugar issues can be one important piece of the puzzle.


Who’s Most at Risk for High Blood Sugar?

Anyone can develop high blood sugar, but some factors increase your risk of prediabetes or diabetes:

  • Family history of type 2 diabetes
  • Carrying extra weight, especially around the abdomen
  • Physical inactivity
  • History of gestational diabetes or delivering a large baby
  • Polycystic ovary syndrome (PCOS)
  • Certain ethnic backgrounds (including African, Hispanic/Latino, Indigenous, South Asian, and Pacific Islander ancestries)
  • High blood pressure, abnormal cholesterol, or fatty liver disease

How Doctors Test for High Blood Sugar

If you recognize several of these symptoms, the next step is not to panic—but to get tested. Common blood tests include:

  1. Fasting plasma glucose – Measures blood sugar after an overnight fast.
    Prediabetes is usually defined as 100–125 mg/dL (5.6–6.9 mmol/L); ≥126 mg/dL (7.0 mmol/L) on two separate tests suggests diabetes.
  2. Hemoglobin A1C – Reflects your average blood sugar over ~3 months.
    Prediabetes: 5.7–6.4%; diabetes: ≥6.5% (on two tests, or with confirmatory testing).
  3. Oral glucose tolerance test (OGTT) – Measures your response to a sugary drink over two hours; often used in pregnancy or when results are borderline.
  4. Random plasma glucose – A spot check, which can support diagnosis when symptoms are severe.
Healthcare professional explaining blood test results to a patient on a tablet
Simple blood tests such as fasting glucose and A1C can reveal whether your symptoms are linked to high blood sugar.

Your clinician may repeat tests to confirm results and rule out temporary causes of high blood sugar, such as acute illness or medications like steroids.


Practical Steps If You Suspect High Blood Sugar

While diagnosis and treatment plans should be guided by a healthcare professional, there are evidence-based lifestyle steps that support healthier blood sugar levels and overall metabolic health.

1. Make an Appointment and Bring a Symptom Log

  • Write down your symptoms, when they started, and how often they happen.
  • Include family history and a list of medications and supplements.
  • Ask specifically about testing for fasting glucose, A1C, and other relevant labs.

2. Focus on Balanced, Fiber-Rich Meals

Research consistently links dietary patterns rich in whole foods, fiber, and healthy fats with better blood sugar control.

  • Build meals around nonstarchy vegetables, lean proteins, and high-fiber carbs (like beans, lentils, oats, quinoa).
  • Limit sugary drinks, refined grains, and ultra-processed snacks where possible.
  • Try pairing carbs with protein and fat to blunt rapid glucose spikes.

3. Move Your Body in Ways That Feel Sustainable

Muscles use glucose for energy. Even modest increases in activity—like a 10–15 minute walk after meals—can improve insulin sensitivity.

  • Aim for at least 150 minutes per week of moderate activity, as tolerated.
  • Include resistance training (such as bodyweight exercises or light weights) 2–3 times weekly if your clinician says it’s safe.

4. Prioritize Sleep and Stress Management

Short sleep and chronic stress are both linked with higher blood sugar and increased diabetes risk.

  • Work toward 7–9 hours of sleep per night, with a consistent schedule.
  • Experiment with stress-relief strategies such as breathing exercises, mindfulness, gentle yoga, or time in nature.

Common Obstacles—and How to Work Around Them

Knowing what to do and actually doing it are two different things. It’s normal to run into barriers.

“I’m afraid of what the tests will show.”

That fear is understandable. But diabetes and prediabetes are far more manageable when caught early. Getting clarity can help you take control instead of wondering in the dark.

“Healthy food feels too expensive or time-consuming.”

Simple, budget-friendly staples like beans, frozen vegetables, oats, eggs, and canned fish can support blood sugar just as well as more expensive options. Batch cooking one or two basic meals can reduce daily stress.

Person preparing fresh vegetables in a kitchen as part of a healthy meal
Even small shifts toward more whole, fiber-rich foods can support steadier blood sugar over time.

“I’m already exhausted—how can I add exercise?”

Start where you are. For many people, a 5–10 minute walk after one meal each day is both realistic and beneficial. As your energy improves, you can build gradually with your clinician’s guidance.


What Recent Research and Guidelines Say

While details evolve year to year, several consistent themes appear in up-to-date guidelines and large studies:

  • Early lifestyle changes in prediabetes can significantly reduce the risk of progression to type 2 diabetes.
  • Weight-neutral approaches that emphasize nutrition quality, movement, and sleep can still improve blood sugar and cardiometabolic health.
  • For people already diagnosed with diabetes, newer medications may not only improve glucose but also reduce cardiovascular and kidney risks.
  • Continuous glucose monitoring (CGM), when available and appropriate, can help some individuals understand how daily habits affect blood sugar in real time.

Listening to Your Body—and Taking the Next Step

High blood sugar often starts quietly, but it doesn’t have to stay invisible. Symptoms like increased thirst, frequent urination, fatigue, blurry vision, slow-healing wounds, tingling in the feet, unexplained weight changes, recurring infections, darkened skin patches, and mood or focus shifts are your body’s way of asking for attention.

Not every symptom means you have diabetes—but they all deserve to be taken seriously. You don’t need to wait until things are “bad enough” to reach out for help.

  1. Make a note of any symptoms that resonated with you.
  2. Schedule an appointment with your healthcare provider and ask about blood sugar testing.
  3. Choose one small, doable habit—like a daily 10-minute walk or adding a serving of vegetables to one meal—to start this week.

You deserve to understand what’s happening in your body and to get care that supports you for the long term. Paying attention to these early signs of high blood sugar is a powerful first step.