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 particularly important 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. Sulfonylurea-induced hypoglycaemia may warrant same-day medical review because recurrence can occur many hours after apparent recovery.
Red flags vs more likely benign
| Feature | More likely benign | Red flag ⚠ |
|---|---|---|
| Consciousness | Alert, orientated, and communicating normally | Drowsy, 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, 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 |
| 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. Consider same-day medical review after any sulfonylurea-induced episode, particularly if it was severe or the cause is unclear.
- 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 confirm and respond to hypoglycaemia alerts according to their diabetes team's guidance.
- 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).
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?
Patients on sulfonylureas who appear to recover after oral glucose may relapse several hours later. Consider same-day GP or diabetes team review after a sulfonylurea-induced episode, particularly if severe or the cause is unclear.
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. Advise the patient to follow current DVLA guidance relevant to their licence type and diabetes treatment before returning to driving. Help them 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 on a glucose-lowering medicine who cannot swallow safely, is confused, or is unconscious requires 999 immediately. Do not attempt to give anything by mouth.
- Mild hypoglycaemia in a conscious patient is treated with 15-20g of fast-acting carbohydrate, rechecked after 10-15 minutes, and followed by 20g of starchy carbohydrate. Sulfonylurea-induced episodes may recur: same-day medical review is recommended.
- Hypoglycaemia unawareness is a significant risk in long-standing diabetes: patients lose warning symptoms and can deteriorate rapidly. They may benefit from access to glucagon following assessment by their diabetes team.