Acute Hypoglycaemia Emergency (< 4.0 mmol/L): The Rule of 15 Step-by-Step for Student Nurses
When a patient with diabetes suddenly becomes shaky, pale, profusely sweaty, or confused, your immediate suspicion must be acute hypoglycaemia. Defined across UK NHS trusts as a capillary blood glucose reading of less than 4.0 mmol/L — “Four is the Floor” — severe hypo episodes require rapid recognition, execution of the Rule of 15, and escalation to prevent seizures, coma, or permanent neurological damage.
“Four is the floor! Never leave a hypoglycaemic patient unattended. Prompt treatment with fast-acting glucose prevents neuroglycopenic deterioration and stabilizes the patient within minutes.”
— Joint British Diabetes Societies (JBDS) Inpatient Guideline
1. Recognition: Adrenergic vs. Neuroglycopenic Symptoms
Hypoglycaemia presents in two distinct stages as blood glucose falls:
Sweating, pallor, tremors, palpitations, hunger, anxiety, restlessness.
Confusion, slurred speech, drowsiness, visual disturbance, seizures, loss of consciousness, coma.
📎 Source: NICE NG18: Type 2 Diabetes — Hypoglycaemia recognition & management
⚠️ Local alert thresholds may vary. Confirm your trust’s hypoglycaemia action level — some sites use <3.5 mmol/L as the trigger. Always follow local policy.
2. Conscious Patient: The Rule of 15
Patient alert and able to swallow safely — execute the standard Rule of 15:
⏱️ THE “RULE OF 15” TREATMENT PATHWAY
ONE option: 4–5 Glucotabs / 150–200mL fruit juice / 1.5–2 tubes Glucogel / 150mL non-diet cola.
Keep patient rested. Retest capillary glucose at exactly 15 minutes.
Still <4.0 mmol/L? Repeat Step 1. After 3 cycles (45 mins) no improvement → call medical team urgently for IV glucose.
Once >4.0 mmol/L: give meal/snack (toast, sandwich, biscuits) to prevent recurrence.
📎 Sources: JBDS Inpatient Hypoglycaemia Guideline | NICE NG18 — Hypoglycaemia Management
⚠️ Approved fast-acting glucose products vary by trust. Check your ward’s emergency hypoglycaemia kit contents — stock products may differ from those listed.
3. Severe Hypo — Unconscious / Unable to Swallow
Patient drowsy, unresponsive, fitting, or aggressive → NO oral treatment — aspiration risk:
🚨 SEVERE HYPO — EMERGENCY ACTIONS
- Stop insulin infusion immediately — pause VRIII/sliding scale pump.
- Call for urgent review — escalate to medical team; dial 2222 if airway/breathing compromised.
- IV access present: 75–100mL of 20% Glucose IV over 15 mins (or 150–200mL 10% Glucose). Flush cannula afterwards.
- No IV access: 1mg Glucagon IM. Note: takes 10–15 mins; may be ineffective in liver disease, starvation, or alcohol excess.
📎 Sources: JBDS — Severe Hypoglycaemia | NICE NG18 — Emergency Treatment
⚠️ IV glucose concentrations and administration protocols vary. Always follow your trust’s prescription chart and emergency drug protocol. Glucagon stock availability and approved route may differ.
4. Referring to the Diabetes Inpatient Specialist Nurse (DISN)
Treating the hypo resolves the emergency — preventing recurrence needs specialist input. Refer to DISN when:
- 2+ hypo episodes during admission
- Severe hypo requiring IV glucose or IM Glucagon
- Impaired hypo awareness — no warning symptoms before drop
- Complex regimens, renal impairment, or feeding/TPN matching difficulties
📎 Source: JBDS — DISN Referral & Prevention of Recurrence
⚠️ Specialist team names and referral pathways differ by trust. Check your hospital intranet for the correct referral form/contact — may be called Diabetes Specialist Nurses, DSN Team, or Inpatient Diabetes Service.
5. Escalation: Word-for-Word SBAR Script
Contacting the medical team or DISN:
- S — Situation: “Student Nurse [Name], [Ward]. [Patient Name] — CBG 2.4 mmol/L, confused and sweating.”
- B — Background: Type 1 Diabetes, admitted with chest infection, ate poorly after Novorapid at breakfast.
- A — Assessment: HR 118, confused, 2 tubes Glucogel given — still 2.6 mmol/L at 15 mins.
- R — Need: Urgent bedside review for IV 20% Glucose, insulin review, DISN referral.
Chest Pain & Suspected STEMI Protocol
10-minute ECG rule, MONA, cardiology escalation.
Published by TheStudentNurse.co.uk — Honest, evidence-based support for every student nurse.
Looking for another emergency protocol?
Head back to the main directory to access rapid guides for STEMI, Sepsis, Hypoglycaemia, Anaphylaxis, and more.
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