Part 3: Symptoms and Diagnosis

What you'll learn

Recognize the classic symptoms of T1D at diagnosis
Understand what diabetic ketoacidosis (DKA) is and why it's dangerous
Know the diagnostic criteria and key lab tests for T1D
Know when to seek emergency medical help

The Classic Symptoms

The destruction of beta cells happens gradually over months or years. But once you cross the tipping point — when your remaining beta cells can no longer keep up — symptoms appear quickly, often within just a few weeks. These are the classic signs:

The "Big Three" (The 3 Polys)

Polydipsia — excessive thirst. You feel like no matter how much water you drink, you can't quench your thirst
Polyuria — frequent urination. You're going to the bathroom far more often than usual, including multiple times at night
Polyphagia — increased hunger. You may feel starving despite eating normally

Other Common Symptoms

Unexplained weight loss — often 3-5 kg or more in a few weeks, despite eating the same or even more
Extreme fatigue — feeling exhausted even with adequate sleep
Blurred vision — caused by fluid changes in the lens of the eye
Slow-healing wounds or frequent infections
Mood changes — irritability, difficulty concentrating
Fruity-smelling breath — a sign of ketone buildup (see DKA section below)

Tip

In children, watch for bedwetting in a child who was previously dry at night. In young children and babies, symptoms can be harder to spot — unexplained irritability, a wet diaper that's heavier than usual, or sudden weight loss should prompt a check.

Scenario: Aisha's Emergency Room Visit

Aisha is 16 years old. Over the past three weeks, she's been drinking water constantly and losing weight. Her parents think it's a growth spurt. On a Saturday morning, she wakes up feeling nauseous. She vomits twice and her breathing becomes deep and rapid. Her breath smells fruity. She's confused and very drowsy.

Her parents rush her to the emergency room. The ER team checks her blood glucose: 480 mg/dL (26.7 mmol/L). Her blood is acidic (pH 7.15, normal is 7.35-7.45). Ketones are highly positive. The diagnosis: diabetic ketoacidosis (DKA) — a life-threatening emergency.

Aisha is treated with IV fluids and insulin. Over the next 24 hours, she stabilizes. The endocrinology team confirms: Type 1 Diabetes.

What Aisha's story teaches us: DKA is often the event that leads to a T1D diagnosis, especially in children and teens. Recognizing symptoms early — before DKA develops — can prevent this dangerous situation.

DKA: The Emergency You Need to Know About

Diabetic ketoacidosis (DKA) happens when the body has little to no insulin. Without insulin, cells can't use glucose for energy, so the body starts breaking down fat at an accelerated rate. This produces ketones — acidic byproducts that accumulate in the blood and make it dangerously acidic.

DKA Warning Signs Decision Card

Use this card to decide when to act:

Sign	What It Means	Action
Blood glucose > 250 mg/dL (13.9 mmol/L) + nausea/vomiting	Possible DKA developing	Check ketones immediately
Moderate to high ketones (blood ketones > 1.5 mmol/L)	DKA is likely	Contact your diabetes team or go to the ER
Deep, rapid breathing (Kussmaul breathing)	Body trying to compensate for acidosis	Go to the ER immediately
Fruity-smelling breath	Ketones being exhaled	Go to the ER immediately

Warning

DKA is a medical emergency. It can progress from "feeling unwell" to life-threatening within hours. When in doubt, always go to the emergency room. It's better to go and be told everything is fine than to wait too long.

How T1D is Diagnosed

If your doctor suspects T1D, they'll run several tests:

Blood Tests

Random blood glucose — a reading of > 200 mg/dL (11.1 mmol/L) with symptoms strongly suggests diabetes
Fasting blood glucose — > 126 mg/dL (7.0 mmol/L) on two separate occasions confirms diabetes
HbA1c (glycated hemoglobin) — > 6.5% (48 mmol/mol) indicates diabetes. This test reflects average blood glucose over the past 2-3 months
Oral glucose tolerance test (OGTT) — 2-hour glucose > 200 mg/dL (11.1 mmol/L) confirms diabetes

Tests That Confirm It's Type 1 (Not Type 2)

Autoantibody panel — presence of GAD65, IA-2, IAA, or ZnT8 autoantibodies confirms autoimmune diabetes
C-peptide — measures how much insulin your pancreas is producing. Very low or undetectable levels confirm T1D
Sometimes genetic testing — HLA typing may be done in research settings

The Diagnostic Timeline

Symptoms appear → Blood glucose test → Diabetes confirmed → Autoantibodies + C-peptide → T1D confirmed → Insulin started immediately

In emergencies (DKA), insulin treatment begins before all confirmatory tests are complete. The priority is saving the patient's life first.

Your Personal Symptom Awareness Checklist

Share this with family, friends, and teachers — early recognition saves lives:

Seek medical attention if you or someone you know has:

Excessive thirst that won't go away
Urinating much more frequently than usual (especially at night)
Unexplained weight loss over days to weeks
Constant fatigue despite adequate rest
Blurred vision
Nausea, vomiting, or abdominal pain with any of the above

Call emergency services immediately if:

Deep, rapid breathing
Fruity-smelling breath
Confusion, difficulty staying awake
Vomiting and unable to keep fluids down

Key takeaways

The classic T1D symptoms are the "3 Polys": excessive thirst, frequent urination, and increased hunger — plus unexplained weight loss and fatigue
Symptoms appear suddenly once ~80-90% of beta cells are destroyed, even though the autoimmune process took months or years
DKA is a life-threatening emergency caused by severe insulin deficiency — know the warning signs and act fast
Diagnosis involves blood glucose tests, HbA1c, autoantibody panels, and C-peptide measurement
Early recognition of symptoms can prevent DKA — share the warning signs with family and friends

Quick Check: The Autoimmune Process

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What does the immune system attack in Type 1 Diabetes?

Symptoms and Diagnosis