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Types of Diabetes Mellitus

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1. Type 1 Diabetes Mellitus (T1DM)

• Accounts for ~5-10% of all diabetes cases
• Typically presents in childhood/young adults, but can occur at any age
• Prone to diabetic ketoacidosis (DKA) - ~30% present with DKA at diagnosis
• Classic symptoms: polyuria, polydipsia, polyphagia, rapid weight loss
• Patients are usually lean at diagnosis
• Requires insulin for survival

• Islet cell antibodies (ICAs)
• Insulin autoantibodies (IAAs)
• Anti-glutamic acid decarboxylase (anti-GAD / GAD65)
• Antibodies to tyrosine phosphatase-related islet antigen 2 (IA-2 / ICA512)

• 1A - Immune mediated (classic, most common)
• 1B - Idiopathic (no evidence of autoimmunity, rare)

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2. Type 2 Diabetes Mellitus (T2DM)

• Most common form of diabetes (~90-95% of cases)
• Typically presents in middle age or older adults, though increasingly seen in younger people due to rising obesity
• Usually asymptomatic for long periods at onset
• Strongly associated with obesity, dyslipidemia, and hypertension (metabolic syndrome)
• Ketosis is rare (some residual insulin secretion remains)
• No association with viral infections or islet autoantibodies
• Peripheral tissue insulin resistance involves defects in muscle glycogen synthesis and insulin receptor function
• Can often be managed initially with lifestyle changes and oral medications

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3. Gestational Diabetes Mellitus (GDM)

• Usually nonketotic hyperglycemia
• Screening recommended at 24-28 weeks of gestation using a 75-g oral glucose load in women with no prior diabetes history
• Reverts to normal in the postpartum period in most cases, but some remain diabetic
• Women with GDM have a 30-67% lifetime risk of developing T2DM
• Post-delivery: all GDM patients should be re-evaluated at 4-12 weeks postpartum using non-pregnant OGTT criteria, then screened at least every 3 years thereafter

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4. Other Specific Types (Secondary Diabetes)

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Prediabetes (Not a separate type, but a recognized risk category)

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Comparison: Type 1 vs Type 2 at a Glance

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• Rosen's Emergency Medicine, Chapter on Diabetes Mellitus
• Tietz Textbook of Laboratory Medicine, 7th Ed. - Box 47.2 Classification
• Creasy & Resnik's Maternal-Fetal Medicine - Classification of Diabetes Mellitus
• Quick Compendium of Clinical Pathology, 5th Ed.
• ADA Standards of Care in Diabetes-2026 (PMID: 41358893) - the latest classification guidelines

2026 Update note: The ADA Standards of Care in Diabetes-2026 (published January 2026) is the most current official classification document. It continues to recognize the same four major categories above, with ongoing refinement in staging criteria for T1DM.

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Hypoglycemia

Definition

• <55 mg/dL (3.1 mmol/L) - symptoms typically begin; further workup indicated in non-diabetic patients
• <50 mg/dL (2.8 mmol/L) - impairment of cerebral function begins
• <40-50 mg/dL - severe symptomatic hypoglycemia in adults
• <20-30 mg/dL (<1.1-1.7 mmol/L) - severe CNS dysfunction

1. Symptoms consistent with hypoglycemia
2. Documented low plasma glucose level
3. Relief of symptoms with correction of hypoglycemia

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Pathophysiology

• Cessation of insulin release
• Release of glucagon (increases hepatic glucose production within minutes)
• Epinephrine (stimulates glycogenolysis + gluconeogenesis, limits peripheral glucose use)
• Cortisol, growth hormone (slower response - hours)

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Symptoms

• Headache, dizziness, blurred vision
• Difficulty concentrating
• Confusion, behavioral changes
• Seizures
• Loss of consciousness, coma
• Death (if severe and prolonged)

Important: The rate of glucose decline matters. A rapid fall may trigger symptoms even before absolute hypoglycemic values are reached, while a gradual decline may produce fewer or no symptoms.

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Causes

By Setting/Patient Type

• Excess insulin (most common): missed meals, reduced carbohydrate intake, excess dose, exercise
• Sulfonylureas and other insulin secretagogues
• Hypoglycemia unawareness (blunted counterregulatory response from prior episodes)
• Renal impairment (decreased drug clearance)

• Alimentary hyperinsulinism (post-gastrectomy, gastrojejunostomy, pyloroplasty, vagotomy) - most common cause
• Post-gastric bypass
• Anti-insulin or anti-insulin receptor antibodies
• Early type 2 diabetes (delayed but exaggerated insulin release)

• Prematurity / small for gestational age
• Maternal diabetes or gestational diabetes mellitus
• Maternal eclampsia / toxemia
• Cold stress, polycythemia, respiratory distress syndrome

• Ketotic hypoglycemia
• Glycogen storage diseases
• Hereditary fructose intolerance, galactosemia
• Leucine hypersensitivity
• Reye syndrome

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Special Situations

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Diagnosis

The OGTT is not appropriate for evaluating suspected fasting hypoglycemia.

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Management

• Oral glucose - sugary foods/beverages (the "15-15 rule" for diabetics: 15g carbohydrates, recheck in 15 min)

• Adults: D50W (dextrose 50%), 1-3 ampules IV (raises glucose by 40-350 mg/dL)
• Children <8 years: D25W (2-4 mL/kg) or D10W - avoid D50W due to hyperosmolarity risk
• If alcohol use disorder is suspected: give thiamine first (before dextrose, to prevent Wernicke's encephalopathy)

• Glucagon 1-2 mg IM or SC - onset 10-20 min, peak at 30-60 min; repeat as needed
• Intranasal glucagon is available but less widely used
• Glucagon is ineffective in alcohol-induced hypoglycemia (depleted glycogen stores)

• Tends to be prolonged and severe
• Observe for at least 24 hours if hypoglycemia recurs after initial treatment
• High-risk: renal impairment, children, drug-naive patients
• Time to hypoglycemia can be delayed up to 18 hours after ingestion

• Aspiration and seizure precautions
• Monitor closely - elderly patients may need several days for full CNS recovery

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Sources

• Rosen's Emergency Medicine - Hypoglycemia chapter
• Tietz Textbook of Laboratory Medicine, 7th Ed. - Box 35.1 Causes of Hypoglycemia
• Henry's Clinical Diagnosis and Management by Laboratory Methods
• Brenner and Rector's The Kidney

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Hypoglycemia - EMT Study Guide

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1. Definition

The brain cannot store or produce its own glucose - it depends entirely on a continuous supply from the blood. This is why hypoglycemia is a true emergency.

1. Symptoms consistent with hypoglycemia
2. Low blood glucose documented
3. Relief of symptoms when glucose is corrected

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2. Causes

In Diabetic Patients (most common)

• Too much insulin - wrong dose, injection without eating
• Missed or delayed meal after taking insulin or oral medications
• Unusual or excessive exercise - muscles consume extra glucose
• Alcohol consumption - blocks the liver from making glucose
• Oral diabetes medications - especially sulfonylureas (e.g., glipizide, glyburide)
• Vomiting or diarrhea after taking medication (food not absorbed)

In Non-Diabetic Patients

EMT Pearl: Always check blood glucose in any patient with altered mental status, seizure, or unconsciousness - regardless of whether they are diabetic.

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3. Signs & Symptoms

Phase 1 - Autonomic (Adrenergic) Symptoms

Phase 2 - Neuroglycopenic Symptoms

Critical EMT Note: Hypoglycemia can mimic stroke (focal weakness, slurred speech, facial droop). Always check BGL before assuming stroke!

Hypoglycemia Unawareness: Some long-term diabetics lose their Phase 1 warning symptoms. They skip straight to unconsciousness without sweating or shakiness - extremely dangerous.

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4. Clinical Assessment

Scene Size-Up

• Is the environment safe?
• Look for medical alert bracelets, insulin pens, glucose meters, glucagon kits, or oral medication bottles
• Ask bystanders: "Is this person diabetic? When did they last eat?"

Primary Survey (ABCs)

Level of Consciousness - AVPU

• Alert
• Verbal response
• Painful response
• Unresponsive

History - SAMPLE

Vital Signs

• Blood pressure - may be mildly elevated or normal
• Heart rate - often tachycardic
• Respirations - usually normal (no Kussmaul breathing like DKA)
• Skin - pale, cool, diaphoretic (key finding)
• Temperature - usually normal

Blood Glucose Level (BGL) - Most Important Test

• Check it EARLY in any patient with AMS, seizure, or suspected diabetic emergency
• Use a glucometer (fingerstick)
• BGL <70 mg/dL = hypoglycemia
• BGL <50 mg/dL = treat immediately

Differentiating Hypoglycemia from Hyperglycemia

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5. Management

Step-by-Step EMT Treatment

SCENE SAFE → BSI → PRIMARY SURVEY → CHECK BGL

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If Patient is CONSCIOUS and CAN SWALLOW (Mild-Moderate)

• Glucose gel (tube) - preferred EMS option
• 4 oz (120 mL) of orange juice or regular soda
• 3-4 glucose tablets
• 1 tablespoon of sugar or honey

1. Give 15 grams of fast-acting carbs
2. Wait 15 minutes
3. Recheck BGL
4. If still <70 mg/dL - repeat
5. Once BGL normalizes, give a complex carbohydrate snack (crackers, sandwich) to prevent rebound

NEVER give oral glucose to an unconscious or unresponsive patient - aspiration risk.

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If Patient is UNCONSCIOUS or CANNOT SWALLOW (Severe)

• Adults: D50W (50% dextrose) 25g IV bolus (one 50 mL ampule)
• Children <8 yrs: D25W (25% dextrose) 0.5-1 g/kg IV, or D10W
• Recheck BGL after 5-10 minutes
• Repeat if needed

• Adults: Glucagon 1 mg IM or SC (deltoid or thigh)
• Onset: 10-20 minutes; Peak: 30-60 minutes
• Can repeat dose
• Also available as intranasal glucagon (Baqsimi) - 3 mg IN

Glucagon DOES NOT work in: Alcohol-induced hypoglycemia (no glycogen stores to mobilize). Give dextrose instead.

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Disposition

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Special Situations for EMTs

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Summary Quick-Reference Card

HYPOGLYCEMIA - EMT QUICK CARD

SUSPECT when: Diabetic + AMS, shaky, pale/sweaty, seizure
CONFIRM with: Glucometer (BGL <70 mg/dL)
CONSCIOUS + swallowing: 15-20g oral glucose → recheck in 15 min
UNCONSCIOUS/no swallow:
  → IV access: D50W 25g IV (adults)
  → No IV: Glucagon 1mg IM/SC
  → Alcohol suspected: Thiamine FIRST
TRANSPORT if: sulfonylurea-induced, no response, unknown cause

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• Rosen's Emergency Medicine - Hypoglycemia, Clinical Features & Management
• Tintinalli's Emergency Medicine - Clinical Features, Diagnosis & Treatment
• Tietz Textbook of Laboratory Medicine, 7th Ed. - Causes of Hypoglycemia
• Henry's Clinical Diagnosis & Management by Laboratory Methods

Altered Mental Status