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Endocrinology & Metabolic

Hypoglycaemia

The brain can neither make nor store glucose, so when circulating insulin outlasts the available carbohydrate the counter-regulatory response cannot keep up and neuroglycopenia follows within minutes.

In a nutshell

Hypoglycaemia in an adult with diabetes is a glucose below 4.0 mmol/L, symptoms or not: four is the floor. Give 15 to 20 g rapid-acting carbohydrate if swallowing is safe, otherwise 100 mL of glucose 20% intravenously over 15 minutes.

Classic presentation

A patient on insulin becomes sweaty, tremulous and then confused some hours after a missed meal, and the capillary glucose is below 4.0 mmol/L.

Key points

  • Looming hypoglycaemia: 4.0 to 6.0 mmol/L on insulin or a sulfonylurea is an alert value, and the Joint British Diabetes Societies (JBDS) suggest intervening below 6.0 mmol/L.
  • The in-hospital glucose target is 6.0 to 10.0 mmol/L; after treating a hypo, aim to restore euglycaemia of 4.0 to 7.0 mmol/L.
  • Severity is not a number. Non-severe means self-treated, severe means someone else had to help. There is no "below 3.0 is severe" band.
  • Chocolate is no longer recommended, because its fat slows carbohydrate absorption. Lucozade was dropped after the 2018 sugar levy changed its carbohydrate content.
  • Glucose 10% and 20% replaced 50%: glucose 10% is 506 mOsm/L against 2522 mOsm/L for 50%, which causes phlebitis and extravasation necrosis.
  • The BNF's 15 to 20 g intravenously and the JBDS 100 mL of glucose 20% are the same dose: glucose 20% contains 20 g per 100 mL.
  • Glucagon is licensed only for insulin-induced hypoglycaemia but is used in practice for sulfonylurea hypoglycaemia. Use caution if anticoagulated: intramuscular bleeding.
  • JBDS 01 covers non-pregnant adults aged 16 and over. Hypoglycaemia in pregnancy is out of its scope and needs obstetric guidance.

First-line investigation

Capillary blood glucose at the bedside, checked during the airway, breathing, circulation, disability, exposure (ABCDE) assessment: below 4.0 mmol/L is hypoglycaemia and is treated before any laboratory result.

Management

Confirm, then stop the insulin infusion

  • Check capillary glucose within the ABCDE assessment. Below 4.0 mmol/L is hypoglycaemia, with or without symptoms. Four is the floor.1
  • Stop any running insulin infusion immediately. Restart it only once the episode is fully treated, and review the rate first.1

Conscious and able to swallow

  • Give 15 to 20 g rapid-acting carbohydrate: 5 to 7 glucose tablets, a 60 mL juice shot, 150 to 200 mL fruit juice, or 3 to 4 teaspoons of sugar in water.1,3
  • Not fruit juice on a low-potassium diet. Not sugar water on acarbose, which blocks the breakdown of sucrose to glucose.1
  • Recheck at 10 to 15 minutes and repeat if still below 4.0 mmol/L, to a maximum of three treatment cycles.1

Conscious but confused or uncooperative

  • Still swallowing: squeeze 2 tubes of 40% glucose gel between the teeth and gums. If ineffective, glucagon 1 mg IM, once only.1,3,4

Unconscious, fitting or unsafe swallow

  • Airway and oxygen first. With access: 100 mL of glucose 20% or 200 mL of glucose 10% IV over 15 minutes, at 400 and 800 mL/hour. Each is 20 g.1,3
  • Hang the whole 100 mL bottle: giving-set dead space means it delivers about 75 mL. Use the smallest volume in renal or cardiac failure.1
  • No access: glucagon 1 mg IM, onset up to 15 minutes. Intravenous glucose is preferred, so keep trying for access; only about 1% respond to a second dose.1,4
  • Recheck at 10 minutes and repeat if still below 4.0 mmol/L. Intramuscular glucagon is given once only.1

When to stop repeating and call

  • Still below 4.0 mmol/L after 30 to 45 minutes or three treatment cycles: call for medical assistance.1
  • Persistent hypoglycaemia: run glucose 10% at 100 mL/hour. Expect recurrence for 24 to 36 hours after a sulfonylurea or long-acting insulin, especially in renal impairment.1

Nil by mouth and tube feeds

  • Nil by mouth: treat as unconscious with IV glucose, then glucose 10% at 100 mL/hour until eating or reviewed.1
  • Enterally fed: the same 15 to 20 g down the tube, each treatment followed by a 40 to 50 mL water flush. Never via a parenteral nutrition line.1

Replace the glycogen, keep the insulin

  • Once above 4.0 mmol/L and recovered: 20 g long-acting carbohydrate. Two biscuits, a slice of toast, 200 to 300 mL dairy milk, or the next meal.1
  • Double to 40 g after glucagon, which has emptied glycogen stores. Insulin pump users may not need it at all.1
  • Do not omit the insulin injection if due. Do not start a variable-rate infusion to stabilise glucose, or chase spikes with stat insulin.1,2

Reduce the dose that caused it

  • Ask the medical team or diabetes specialist nurse to reduce the insulin or sulfonylurea dose active at the time, not the next one.1
  • Continue capillary glucose monitoring for at least 24 to 48 hours, at home if discharged. Give education, a rescue plan and carer glucagon teaching.1,2
  • Driving: none at 4.0 mmol/L or below; carbohydrate first at 4.0 to 5.0 mmol/L; wait 45 minutes from 5.0 mmol/L before driving.6
  • Group 1 drivers notify the Driver and Vehicle Licensing Agency (DVLA) after two severe episodes while awake in 12 months, Group 2 after one.6

Exam traps

  • Do not omit the insulin injection that is due. It is not the dose that caused the hypo, and omitting it invites ketoacidosis.
  • Symptoms above 4.0 mmol/L are not hypoglycaemia. Give a carbohydrate snack; the threshold for brain dysfunction is not reset upwards by poor control.
  • Glucagon mobilises hepatic glycogen, so it fails in exactly the patients who present: starved, malnourished, alcohol-dependent or with liver disease.
  • Only about 1% respond to a second glucagon injection. Keep trying for intravenous access rather than repeating the dose.
  • Never put oral carbohydrate into the mouth of an unconscious patient. The 40% glucose gel pathway is for a confused patient who can still swallow.
  • Whether an in-hospital episode needing third-party help affects a licence is unresolved: JBDS 01 records that DVLA clarification is awaited.

Illustrations

Emergency glucagon kit for severe hypoglycaemiaAn emergency glucagon kit with vial, syringe and preparation instructions, used when severe hypoglycaemia causes impaired consciousness and oral carbohydrate is unsafe.Mr Hyde, Wikimedia Commons · Public domain

Key sources

  1. Joint British Diabetes Societies for Inpatient Care (JBDS-IP), The Hospital Management of Hypoglycaemia in Adults with Diabetes Mellitus (JBDS 01, sixth revision, January 2023. Scope is non-pregnant adults aged 16 years and over in hospital. Source of the 4.0 mmol/L threshold, the 4.0 to 6.0 mmol/L looming-hypoglycaemia alert range, the 6.0 to 10.0 mmol/L in-hospital target, algorithms A to E and appendix 5)Updated 1 Jan 2023
  2. NICE, Type 1 diabetes in adults: diagnosis and management (NG17, published August 2015 and last updated August 2022. Cited for hypoglycaemia awareness assessment, structured education, regimen review and glucose-monitoring technology in type 1 diabetes, not for any dose in this chapter)Published 26 Aug 2015 | Updated 17 Aug 2022
  3. BNF, Glucose (BNF monograph, Indications and dose: hypoglycaemia in adults by mouth (15 to 20 g), by buccal administration (1.5 to 2 tubes of glucose 40% oral gel) and by intravenous infusion (15 to 20 g over 15 minutes as glucose 10% or 20%))
  4. BNF, Glucagon (BNF monograph, Indications and dose: diabetic hypoglycaemia, adult 1 mg by subcutaneous or intramuscular injection, with intravenous glucose required if there is no response within 10 minutes; cautions record that glucagon is ineffective in chronic hypoglycaemia and starvation)
  5. Endocrine Society, Evaluation and Management of Adult Hypoglycemic Disorders: An Endocrine Society Clinical Practice Guideline (J Clin Endocrinol Metab 2009;94(3):709. Recommendation 1.1 (evaluate only where Whipple's triad is documented) and recommendation 2.1 (measure plasma glucose, insulin, C-peptide, proinsulin and beta-hydroxybutyrate and screen for oral hypoglycaemic agents during a spontaneous episode). Used because no UK guideline covers hypoglycaemia in a person without diabetes)
  6. Driver and Vehicle Licensing Agency (DVLA), A guide to insulin treated diabetes and driving (INF294, edition 10/25. Source of the 4.0 mmol/L do-not-drive level, the 4.0 to 5.0 mmol/L snack rule, the 45-minute wait from 5.0 mmol/L, the 2-hourly checking interval and the Group 1 and Group 2 notification rules)

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.