Hypoglycaemia: Recognising and Responding to Low Blood Sugar
How community pharmacists can recognise hypoglycaemia, distinguish mild from severe episodes, treat safely in pharmacy, and know when to call 999.
Why this matters
Hypoglycaemia (low blood glucose) is one of the most common acute medical emergencies encountered in community pharmacy. It occurs most commonly with insulin, sulfonylureas, and meglitinides. It may also occur with other glucose-lowering medicines when combined with these agents or when food intake is significantly reduced. Community pharmacists supply these medicines daily and are well placed to provide immediate assistance when a hypoglycaemic episode occurs nearby.
The distinction between mild and severe hypoglycaemia determines the correct response. A conscious patient who can swallow safely may be managed in the pharmacy with oral glucose. A patient who is unconscious, seizing, or unable to swallow safely requires 999 immediately: nothing should be placed in the mouth. Errors in this distinction can be fatal.
Hypoglycaemia unawareness is a significant risk. Patients with long-standing diabetes may lose the adrenergic warning symptoms that normally alert them to falling glucose. Without sweating, trembling, or palpitations to warn them, they may deteriorate rapidly from near-normal function to unconsciousness. These patients may benefit from access to glucagon and should discuss this with their diabetes team.
Sulfonylurea-induced hypoglycaemia carries an additional risk: because the drug continues to stimulate insulin secretion for many hours, hypoglycaemia can recur even after the episode appears to have resolved with oral glucose. This risk is greater in older adults, those with chronic kidney disease, those on long-acting preparations, and those living alone. These patients should be referred for same-day medical review after any sulfonylurea-induced episode.
Red flags vs More likely benign
| Feature | More likely benign | Red flag ⚠ |
|---|---|---|
| Consciousness | Alert, orientated, and communicating normally | Drowsy, severely confused, aggressive, difficult to rouse, or unconscious |
| Symptoms | Mild sweating, slight trembling, hunger, or palpitations | Severe shaking, profound sweating, pallor, seizure, or loss of consciousness |
| Ability to swallow | Can swallow safely and cooperate with oral treatment | Unable to swallow safely, unable to cooperate with oral treatment, choking risk, or unconscious: do not give anything by mouth |
| Blood glucose | 4.0 mmol/L or above on a glucose-lowering medicine | Below 4.0 mmol/L on a glucose-lowering medicine, or rapidly falling with symptoms |
| Response to treatment | Glucose rising and symptoms improving within 15 minutes | No improvement after two rounds of oral carbohydrate, or glucose remaining below 4.0 mmol/L after repeat treatment |
| Driving or alone | Support available; not driving; glucose checked before driving | Episode occurred while driving or operating machinery, or patient found alone and confused |
| Medicine risk | On low-risk glucose-lowering medicine or well-controlled insulin | On long-acting insulin, high-dose sulfonylurea, or previous history of severe hypoglycaemia |
| Recurrent episodes | Occasional mild episode with identifiable cause | Recurrent hypoglycaemia without clear cause: should always prompt review of diabetes management by the GP or diabetes team |
Key Clinical Points
The following points are important when assessing any patient with suspected hypoglycaemia.
- A blood glucose below 4.0 mmol/L on a glucose-lowering medicine generally requires treatment even if the patient currently feels well, as glucose can fall further without warning.
- Hypoglycaemia unawareness: patients with long-standing diabetes may lose adrenergic warning symptoms (sweating, trembling, palpitations) and deteriorate rapidly without early signs. These patients may benefit from access to glucagon following assessment by their diabetes team.
- SGLT2 inhibitors (empagliflozin, dapagliflozin, canagliflozin, ertugliflozin) do not themselves cause hypoglycaemia when used alone. If a patient on an SGLT2 inhibitor alone develops hypoglycaemia, assess for an alternative cause.
- Sulfonylurea-induced hypoglycaemia can recur for many hours after apparent recovery because the drug continues to stimulate insulin secretion. Same-day medical review is recommended after any sulfonylurea-induced episode, particularly in older adults, those with chronic kidney disease, long-acting sulfonylurea preparations, recurrent episodes, or patients living alone.
- Declining kidney function increases the risk of hypoglycaemia, particularly with insulin and sulfonylureas, as reduced clearance can cause drug accumulation. Be alert to this risk in older patients and those with known chronic kidney disease.
- Treat presumed hypoglycaemia even without a glucose reading: if a patient taking insulin or a sulfonylurea develops sweating, tremor, confusion, or unusual behaviour and blood glucose cannot immediately be checked, treat as presumed hypoglycaemia while arranging appropriate assessment.
- Sudden confusion, aggression, unusual behaviour, or reduced concentration in a patient treated with insulin or sulfonylureas should always raise suspicion of hypoglycaemia. Do not assume a behavioural or psychiatric cause without first considering glucose.
- Patients using continuous glucose monitoring should respond to hypoglycaemia alerts according to their diabetes team guidance. If symptoms suggest hypoglycaemia but the sensor reading does not match, use a finger-prick capillary blood glucose check where possible. Do not delay treatment if the patient is symptomatic.
- Patients at increased risk of severe or recurrent hypoglycaemia include: older adults, those with long-standing diabetes or hypoglycaemia unawareness, chronic kidney disease, cognitive impairment, previous severe hypoglycaemia, insulin or sulfonylurea therapy, and those living alone. Lower the threshold for escalation in these patients.
Medicines most likely to cause hypoglycaemia: all insulin preparations, sulfonylureas (gliclazide, glibenclamide, glipizide, tolbutamide), and meglitinides (repaglinide, nateglinide).
🛑 SUGAR: Pharmacy Response Framework
Use this framework for any patient with suspected hypoglycaemia.
Sweating, trembling, pallor, confusion, or unusual behaviour on a glucose-lowering medicine: act now. Check blood glucose if possible.
Call 999 immediately. Do not put anything in the mouth. Place in the recovery position if breathing normally.
Treat promptly with 15-20 g of fast-acting carbohydrate if the patient can swallow safely and cooperate with oral treatment.
Give 15-20 g of fast-acting carbohydrate (glucose gel, fruit juice, or glucose tablets; check the product label for the number of tablets required as this varies by brand). Recheck blood glucose after 10-15 minutes. Repeat if still below 4.0 mmol/L.
Once above 4.0 mmol/L and symptoms resolved, give the next meal if due, or a longer-acting carbohydrate snack such as a sandwich, biscuits, or cereal. Do not drive until glucose has recovered to at least 5.0 mmol/L and at least 45 minutes have passed. Identify the cause and plan prevention.
Key Questions to Ask
These questions help identify the cause, assess severity, and determine ongoing risk.
- What glucose-lowering medicines is the patient taking? Insulin and sulfonylureas carry the highest hypoglycaemia risk.
- When did they last eat, and was the meal smaller than usual? Missed or reduced meals are the most common precipitant.
- Has there been more physical activity than usual, including walking, housework, or exercise? Physical activity increases glucose consumption.
- Have they consumed alcohol? Alcohol suppresses gluconeogenesis and can cause prolonged hypoglycaemia, particularly overnight.
- Has there been a recent change in dose, a new medicine added, or a change in eating pattern?
- Any acute illness, vomiting, or significantly reduced food intake? These can increase hypoglycaemia risk, particularly in insulin-treated patients.
- Any recent significant weight loss? Weight loss can reduce insulin requirements and increase the risk of hypoglycaemia if doses have not been adjusted.
- Do they normally get warning symptoms before their glucose falls? Absence of warning symptoms suggests hypoglycaemia unawareness.
- Has this happened before? How did they manage it? Did they recover fully?
- Are they alone? Who is available to stay with them while they recover or until help arrives?
Sulfonylurea-induced hypoglycaemia in older adults, patients with chronic kidney disease, those on long-acting preparations, recurrent episodes, or patients living alone requires same-day GP or diabetes team review because relapse can occur after apparent recovery.
What to do in pharmacy
Do not leave the patient alone until blood glucose has recovered above 4.0 mmol/L and they are clinically stable.
Driving: the patient should not resume driving until glucose has recovered to at least 5.0 mmol/L and at least 45 minutes have passed, because cognitive recovery lags behind glucose correction. Severe hypoglycaemia, impaired awareness of hypoglycaemia, or an episode occurring while driving may require DVLA notification depending on licence type and treatment. Advise the patient to check current DVLA guidance for their licence category.6
Help the patient identify the cause of the episode (missed meal, extra activity, incorrect dose, alcohol) and plan to prevent recurrence. Remind patients at risk to carry fast-acting glucose at all times. Patients who may benefit from glucagon should be directed to their GP or diabetes team to discuss supply and training. Recurrent hypoglycaemic episodes should always prompt a review of the patient's diabetes management.
Key takeaways
- A patient who is unconscious, having a seizure, cannot swallow safely, cannot cooperate with oral treatment, or is severely confused requires 999 immediately. Do not attempt to give anything by mouth.
- Mild hypoglycaemia in a conscious patient is treated with 15-20 g of fast-acting carbohydrate, rechecked after 10-15 minutes, and followed by a longer-acting carbohydrate snack. Sulfonylurea-induced episodes may recur: same-day medical review is recommended, especially in older adults and those with chronic kidney disease.
- Do not drive until glucose is at least 5.0 mmol/L and at least 45 minutes have passed. Patients with hypoglycaemia unawareness lose warning symptoms and can deteriorate rapidly: lower the threshold for escalation and ensure they have access to glucagon following assessment by their diabetes team.
📚 References
- Joint British Diabetes Societies for Inpatient Care. The hospital management of hypoglycaemia in adults with diabetes mellitus. 4th ed. JBDS-IP; 2023. https://abcd.care/sites/abcd.care/files/site_uploads/JBDS_02_Hypo_Adults_Revised.pdf
- National Institute for Health and Care Excellence. Hypoglycaemia. NICE Clinical Knowledge Summary. London: NICE; 2022. https://cks.nice.org.uk/topics/hypoglycaemia/
- National Institute for Health and Care Excellence. Type 1 diabetes in adults: diagnosis and management. NG17. London: NICE; 2022. https://www.nice.org.uk/guidance/ng17
- National Institute for Health and Care Excellence. Type 2 diabetes in adults: management. NG28. London: NICE; 2022. https://www.nice.org.uk/guidance/ng28
- Joint Formulary Committee. Glucagon. British National Formulary. London: BMJ Group and Pharmaceutical Press. https://bnf.nice.org.uk/drugs/glucagon/
- Driver and Vehicle Licensing Agency. A guide to insulin treated diabetes and driving. GOV.UK. https://www.gov.uk/government/publications/information-for-health-professionals-on-insulin-treated-diabetes-and-driving
Download the checklist
Continuing professional development
Test your knowledge
Answer 10 questions on this article. Score 70% or more and you will receive a dated, verifiable certificate for 1 hours of CPD, ready for your portfolio.
Disclaimer: For educational use by healthcare professionals only. Does not replace clinical judgement, local pathways, or NICE guidance. Not for public self-diagnosis.