Our brains rely on glucose, so if glucose levels drop a lot, it can start to affect brain function²²⁵. This is a condition called hypoglycemia²²⁶, which has two categories:

• Mild or moderate, which can likely be self-treated
• Severe, which can, in certain instances, require help from another person for recovery

Recognizing hypoglycemia when it happens

When do you start feeling symptoms of hypoglycemia?

In general, people will start to experience symptoms of hypoglycemia when their glucose level is under 4.0 mmol/L. When glucose levels fall below 2.8 mmol/L, a person can lose consciousness and will need the assistance of another person²²⁷.

Common symptoms of hypoglycemia include:

How does hypoglycemia affect people experiencing it?

Hypoglycemia can²²⁸:

• Provoke tense-tiredness (a feeling of being both tense and tired at the same time) and feelings of unhappiness 
• Increase irritability and anger
• Make us pessimistic about everyday situations and about life issues
• Lead to mood changes, which are negative, stressful and unpleasant
• Lead to anxiety (with repeated episodes of hypoglycemia)

Hypoglycemia can also cause cognitive (mental) impairment. Studies have shown that mental function can be affected when glucose levels fall below 3.0 mmol/L. Below this level, people with diabetes may start to experience problems with²²⁵:

• Fine motor coordination
• Mental speed
• Concentration
• Certain memory functions (e.g., word recall, working memory)

Finally, hypoglycemia can cause some uncommon but serious consequences to other parts of the body including the brain (coma, seizures, mental impairment, psychological effects²²⁵), bones (falls, accidents, dislocations, driving mishaps²²⁵), and the heart (angina or chest pains, abnormal heart rhythms, heart failure^225,229).

What are the causes and risk factors for hypoglycemia?

Causes²³⁰ that may lead to hypoglycemia include:

• Insufficient food or missed meals (most common cause)
• Taking too much insulin or sulfonylurea medication
• Alcohol consumption (especially if you haven’t eaten)
• Physical exercise
• Delayed emptying of the stomach

Risk factors^231,232 that may make hypoglycemia more likely include:

• Increasing age
• Duration of type 1 diabetes
• Duration of treatment with insulin in people with type 2 diabetes
• Previous episodes of severe hypoglycemia (most powerful predictor of future episodes)
• Impaired awareness of hypoglycemia
• Kidney disease
• Decreased mental ability (e.g., depression)
• Strict control of blood glucose
• Increased glucose variability