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Understand your high blood sugar symptoms
Evidence-based guides on blood sugar symptoms, levels, and management — plus an app to track it all.
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The short version
What are the symptoms of high blood sugar?
The most common symptoms of high blood sugar are increased thirst, frequent urination — especially at night — fatigue that sleep does not fix, blurred vision, headaches, increased hunger, slow-healing cuts, and recurrent thrush or urinary infections. Most people begin to notice them once glucose stays above roughly 180–200 mg/dL (10–11 mmol/L), though many with prediabetes and early type 2 diabetes feel completely well.
Vomiting, deep or rapid breathing, fruity-smelling breath, or confusion alongside a high reading is a medical emergency — those signs point to diabetic ketoacidosis and need urgent care rather than a wait-and-see.
- Earliest signs
- Thirst, frequent urination at night, and fatigue after meals.
- Where symptoms usually start
- Above roughly 180–200 mg/dL (10–11 mmol/L), where the kidneys begin spilling glucose.
- Emergency signs
- Ketones, vomiting, rapid breathing, fruity breath, confusion.
Start here
Four questions people ask before anything else
Each guide is written to answer one question properly rather than skim five. Start with whichever sounds like your week.
Symptoms6 min read
Prediabetes Symptoms: The Signs Most People Never Notice
The honest headline is that prediabetes usually causes nothing. Roughly 1 in 3 US adults has it and around 8 in 10 of them do not know. Here is what does show up, and who should be tested regardless.
Management6 min read
Prediabetes Diet: What to Eat, What to Avoid, and Why Order Matters
There is no prediabetes food list that works on its own. What moves numbers is the shape of the plate, the order you eat it in, and what you walk off afterwards.
Symptoms8 min read
High Blood Sugar Symptoms: 12 Warning Signs You Shouldn't Ignore
Hyperglycemia rarely announces itself. It shows up as thirst you keep topping up, an afternoon that flattens you, and vision that blurs for a week. Here are the 12 signs worth knowing.
Levels7 min read
Normal Blood Sugar Levels Chart: Fasting, After Eating & A1c
One number rarely means much on its own. Here is what normal looks like fasting, two hours after eating and on an A1c test — and where the thresholds for prediabetes and diabetes actually sit.
Companion app for iPhone
Snap your meals and see what they do to your blood sugar
T1dApp turns food photos and glucose readings into clear, everyday patterns. Get carbs in seconds, an estimate of your blood sugar 2 hours later, and Dexcom and Libre readings through Apple Health.
- Snap meals with AI: see carbs, calories, and an expected 2-hour glucose range.
- Apple Health sync: import Dexcom and FreeStyle Libre CGM readings automatically.
- Meal impact insights: see which foods spike your blood sugar and which barely move it.
- Estimated A1c & reports: export clean PDF or CSV summaries to hand your care team.
Download on theApp Store
iPhone & iPad · Built for Type 1, Type 2, and Prediabetes
Latest
Recently published and updated
Every guide carries a last-reviewed date. If it is stale, we either update it or take it down.
Causes6 min read
Stress and Blood Sugar: How Cortisol Raises Glucose Without Food
Cortisol and adrenaline raise glucose by design, telling the liver to release its stores. Your body cannot tell a deadline from a predator, which is why readings climb on days you have not eaten anything unusual.
Symptoms6 min read
Prediabetes Symptoms: The Signs Most People Never Notice
The honest headline is that prediabetes usually causes nothing. Roughly 1 in 3 US adults has it and around 8 in 10 of them do not know. Here is what does show up, and who should be tested regardless.
Management6 min read
Prediabetes Diet: What to Eat, What to Avoid, and Why Order Matters
There is no prediabetes food list that works on its own. What moves numbers is the shape of the plate, the order you eat it in, and what you walk off afterwards.
Levels5 min read
Normal Blood Sugar Levels by Age: What Actually Changes
Most by-age charts are misleading. The thresholds are identical for every adult; what legitimately loosens with age is the target you are given once diagnosed, and the reason is hypoglycemia risk.
Symptoms5 min read
High Blood Sugar Symptoms in Women: Signs That Get Missed
Thirst and fatigue look the same in everyone. What differs for women is the cluster around them — recurrent thrush, urinary infections, cycle-linked swings — and how often those get treated one at a time without anyone checking glucose.
Levels6 min read
Fasting Blood Sugar Levels: Normal Range and What Yours Means
Normal is 70 to 99 mg/dL, prediabetes starts at 100 and diabetes at 126. But the number is only as good as the fast behind it — and morning readings mislead more often than any other measurement.
Quick reference
Blood sugar levels, without the guesswork
Normal, prediabetes and diabetes ranges for fasting, post-meal, A1c and random tests — switch between mg/dL and mmol/L, and see the thresholds that actually matter.
Fasting blood sugar
Measured after at least 8 hours without food or drink other than water — usually first thing in the morning.
Normal
A typical healthy fasting range.
70–99 mg/dL3.9–5.5 mmol/L
Prediabetes (impaired fasting glucose)
Higher than normal, not yet diabetes. Often reversible.
100–125 mg/dL5.6–6.9 mmol/L
Diabetes range
Needs a repeat test on a separate day to confirm.
126 mg/dL or above7.0 mmol/L or above
Ranges follow standard diagnostic criteria for non-pregnant adults. Your own targets may differ — pregnancy, age, kidney disease and certain medications all change the picture. Always confirm your targets with your healthcare provider.
Blood sugar 2 hours after eating
Measured two hours after the first bite of a meal, or two hours into a glucose tolerance test.
Normal
Most people peak under 140 even after a large meal.
Below 140 mg/dLBelow 7.8 mmol/L
Prediabetes (impaired glucose tolerance)
Post-meal numbers often rise before fasting ones do.
140–199 mg/dL7.8–11.0 mmol/L
Diabetes range
A repeat abnormal result confirms the diagnosis.
200 mg/dL or above11.1 mmol/L or above
Ranges follow standard diagnostic criteria for non-pregnant adults. Your own targets may differ — pregnancy, age, kidney disease and certain medications all change the picture. Always confirm your targets with your healthcare provider.
A1c (HbA1c)
A blood test that reflects your average blood sugar over roughly the previous two to three months.
Normal
Average glucose roughly below 117 mg/dL.
Below 5.7%(Below 39 mmol/mol)
Prediabetes
Roughly 117–137 mg/dL average glucose.
5.7–6.4%(39–46 mmol/mol)
Diabetes range
Roughly 140 mg/dL average glucose or higher.
6.5% or above(48 mmol/mol or above)
Ranges follow standard diagnostic criteria for non-pregnant adults. Your own targets may differ — pregnancy, age, kidney disease and certain medications all change the picture. Always confirm your targets with your healthcare provider.
Quick answers
61 questions, answered in two sentences
Short pages for the specific things people search at 2am. Each one links up to the guide that covers it properly.
- Can a hot shower raise blood sugar?
- Can an infection raise blood sugar?
- Can cinnamon lower blood sugar?
- Can coffee raise blood sugar?
- Can dehydration raise blood sugar?
- Can high blood sugar cause anxiety or mood changes?
- Can high blood sugar cause blurred vision?
- Can high blood sugar cause headaches?
- Can high blood sugar make you dizzy?
- Can high blood sugar make you itch?
- Can lack of sleep raise blood sugar?
- Can protein raise blood sugar?
Topics
Browse by what you need
- Symptoms
What high blood sugar actually feels like, early and late.
- Levels
Fasting, post-meal and A1c numbers, and what they mean.
- Management
Practical, evidence-based ways to bring readings down.
- Causes
Why your numbers climb — food, stress, sleep, illness, hormones.
- Emergencies
Warning signs that need urgent care, not a wait-and-see.