Hypoglycaemia

Video overview

This video walks through the key concepts covered on this page.

What glucose level counts as a hypo?

Physiologically, hypoglycaemia is a glucose level below 3.3 mmol/L (60 mg/dL). People without diabetes typically sit between 3.3 and 6.7 mmol/L (60 and 120 mg/dL) throughout the day.

In practice, 4.0 mmol/L (70 mg/dL) is the standard treatment threshold, and there is a good reason for this. In modern CGM accuracy studies, a reading in the low range is considered accurate if it falls within 0.8 mmol/L (15 mg/dL) of true blood glucose measured with lab-grade comparators such as YSI.

The mechanism: if true blood glucose is 3.2 mmol/L (58 mg/dL), a CGM can read up to approximately 0.8 mmol/L higher and still be labelled accurate. That puts the CGM display near 4.0 mmol/L (70 mg/dL). Setting the low alert and treatment threshold at 4.0 mmol/L therefore tends to catch almost all true hypos before they become physiologically dangerous.

If the alert were set at 3.3 mmol/L (60 mg/dL), a “safe” CGM error could mask a true glucose level of around 2.6 mmol/L (47 mg/dL) with no alarm. Many people find this is too narrow a margin.

Why pure glucose is the fastest treatment

Pure glucose starts raising blood glucose in about 10 minutes and has largely done its job by approximately 20 minutes. That is why the standard recheck point is 20 minutes, not 5 or 10.

Why body weight matters for dosing

Body weight is a rough proxy for blood volume and muscle mass. Larger bodies have more blood to fill with glucose and more tissue pulling glucose from the blood, especially after heavy bolus insulin or exercise. Treatment therefore tends to scale with weight.

This chart shows a simple weight-based guide:

Why cap treatment at approximately 18 to 20 grams? The intestine absorbs glucose at about 1 gram per minute. Taking more than roughly 20 grams and rechecking at 20 minutes tends to stack unabsorbed glucose in the gut, which often causes a delayed spike and sometimes gastrointestinal discomfort. A sensible first dose followed by a repeat if still low tends to produce cleaner results.

Why glucose tablets tend to work best

• Cheap, portable, and stable (they do not go off).
• Small, consistent doses (usually 3 to 4 grams per tablet), easy to split for precision.
• Treating a hypo is medicine, not a snack. “Tasty treats” tend to blur that line and can drive overeating loops.
• Liquid “glucose” drinks (Lucozade, Gatorade, and similar) are messy: formulations change, some use mixed sugars, they are bulky, hard to measure precisely, and often expensive.
• For faster swallowing, many people find that taking glucose tablets with water works well.

Using trend arrows for prevention

Treatment can differ depending on whether a hypo is already happening or is being prevented, and whether the CGM arrow is flat, single-down, or double-down. The full decision table lives in Dynamic Glucose Management, specifically the MATCH section of GAME-SET-MATCH.

Why sugar treatments overshoot: dose stacking, not pharmacology

A controlled 10 to 15g dose of sucrose (e.g. Skittles) recovers glucose at 15 minutes in 88% of attempts, equivalent to glucose tablets (Husband 2010, paediatric RCT). The common experience of sugar “taking an hour” is driven by dose stacking: larger servings, repeated treatments before the first has been absorbed, and uncounted food eaten alongside. Fructose-heavy treatments (juice, fruit bars) are genuinely slower and fail to recover glucose in about one-third of attempts.

The mechanism: table sugar (sucrose) is glucose plus fructose in equal parts. At small doses, the glucose half acts quickly and the treatment works. The problem comes when doses are larger or repeated: the fructose half goes to the liver and can trigger hunger and overeating cascades. That is one reason unconstrained sugar treatments so often end in rebound highs; it is a dosing problem, not an inherent problem with sucrose at controlled amounts.

Are temporary basal reductions useful for hypos?

Temporary basal changes are the slowest mover of glucose. They tend to be too delayed to prevent or treat an imminent hypo. This is explored in more depth on the basal insulin page.

Impaired awareness of hypoglycaemia

About 15 to 30 per cent of adults with type 1 diabetes develop impaired awareness of hypoglycaemia (IAH), where warning symptoms such as shaking, sweating, and confusion become muted or absent (Geddes 2008). This matters because IAH increases the risk of severe hypoglycaemia approximately sixfold (Gold 1994).

The good news: awareness can often be restored by strict avoidance of glucose levels below 4.0 mmol/L for several weeks (Cranston 1994). This is sometimes called “hypo avoidance” or reversing HAAF (hypoglycaemia-associated autonomic failure). It requires close work with your diabetes care team and is one of the strongest arguments for setting CGM alerts conservatively.

How AID systems reduce hypoglycaemia

Automated insulin delivery systems with low-glucose suspend (LGS) or predictive low-glucose management (PLGM) are specifically designed to reduce hypoglycaemia without raising average glucose. LGS reduces nocturnal hypo exposure by approximately 37.5 per cent (Bergenstal, ASPIRE 2013). PLGM reduces time below target by 50 to 54 per cent (Buckingham 2015). This is one of the clearest clinical advantages of AID technology, particularly overnight.

Severe hypoglycaemia: glucagon rescue

Severe hypoglycaemia means the person cannot treat themselves and needs help from someone else. For these situations, glucagon rescue options are now available that are significantly easier for bystanders to use than the older reconstitution kits:

• Intranasal glucagon (Baqsimi): a single nasal spray, no injection needed.
• Glucagon autoinjector (Gvoke): a pre-filled pen, ready to use without mixing.

Discuss a rescue plan with your care team. Everyone who spends time with someone at risk of severe hypoglycaemia should know where the glucagon is and how to use it.