4.2 Identify the causes of hypoglycaemia

This guide will help you answer 4.2 Identify the causes of hypoglycaemia.

Hypoglycaemia means low blood glucose. Glucose, also called blood sugar, is the body’s main source of energy. It fuels every cell, especially in the brain. When glucose drops below normal levels, problems can happen quickly.

For most adults, hypoglycaemia begins when blood glucose falls below 4 millimoles per litre (mmol/L). If it is not treated, it can lead to confusion, unconsciousness, seizures, or even death. People with diabetes are most at risk, but others can develop hypoglycaemia too.

Knowing what causes hypoglycaemia helps prevent it and ensures people stay well. If you work in health or social care, understanding the causes keeps people safe.

The Body’s Control of Blood Sugar

The body keeps blood sugar within a narrow range. Hormones like insulin and glucagon manage these levels.

Insulin: Made in the pancreas, insulin lowers blood sugar by helping glucose enter cells for energy.
Glucagon: Also made in the pancreas, glucagon raises blood sugar by telling the liver to release stored glucose.
If these hormones get out of balance, blood sugar can fall too low.

If a person has diabetes, things become complicated. Treatments like insulin or tablets make the body sensitive to low sugar levels. Mistakes or changes in routine can cause hypoglycaemia.

Main Causes of Hypoglycaemia

Below are the main causes, covering both people with and without diabetes. Each cause links to changes in a person’s routine, health, or medication.

Medications

Most cases of hypoglycaemia happen in people with diabetes. Medication is often the reason.

Insulin

Insulin is an injected medicine. If someone takes too much, misses a meal, or exercises more than normal, blood sugar can plunge. Sometimes, the amount of insulin given is not adjusted for new activities, illness, or changes in diet.

Tablet Medications for Diabetes

Some diabetes tablets lower blood sugar. The main ones are sulfonylureas (like gliclazide, glipizide) and meglitinides (like repaglinide). Taking these without food or in incorrect doses can lower blood sugar too much.

Other tablets, such as metformin, rarely cause hypoglycaemia on their own, but combined with other diabetes medicines, risk increases.

Other Medicines

Sometimes, medicines unrelated to diabetes upset blood sugar control. These include:

Quinine, used for malaria
Pentamidine, used for pneumonia in people with weakened immune systems
Some antibiotics and heart medicines

Always check the side effects of medicines taken by those you support.

Dietary Causes

Food intake directly affects blood sugar. Eating patterns are key.

Missed or Delayed Meals

If a person takes insulin or diabetes tablets and then skips a meal, blood sugar can drop. This is one of the most common causes in social care settings. People reliant on others for meal prep are especially at risk.

Not Eating Enough Carbohydrates

Carbohydrates, found in bread, rice, pasta, potatoes, and fruit, become glucose in the body. If a meal is too small or has no carbohydrates, this can cause hypoglycaemia, especially for people on diabetes medication.

Vomiting or Diarrhoea

Repeated vomiting or diarrhoea means food is not absorbed. This can lead to missed calories and glucose, while medication continues to act, leading to low blood sugar.

Changes in Physical Activity

Exercise uses glucose for energy. If a person exercises more than usual, particularly without extra food or medication adjustment, the risk of hypoglycaemia increases. Even light activity, such as gardening or walking, can make a difference in older people or those not used to being active.

Alcohol

Alcohol prevents the liver from releasing stored glucose. If someone drinks alcohol, especially without food, their risk of hypoglycaemia goes up. The effect can happen during drinking or many hours later, even the next morning. Those taking insulin or sulfonylureas are most at risk.

Illness and Health Conditions

Some illnesses make hypoglycaemia more likely. These can happen in people with or without diabetes.

Kidney Disease

Damaged kidneys may not break down medicines properly, so drugs like insulin stay in the body longer. This can make hypoglycaemia more likely.

Liver Disease

The liver stores and releases glucose as needed. If the liver is damaged (for example, with hepatitis or cirrhosis), it may not release glucose, leading to hypoglycaemia.

Hormone Disorders

Conditions that affect hormone production can upset glucose control, including

Addison’s disease: affects adrenal glands, leading to low levels of cortisol and other hormones needed for glucose balance
Low pituitary hormones

Sepsis and Infections

Very severe infections (sepsis) use up lots of body energy. The liver may not keep up with glucose demands, so blood sugar drops. This is a rare but dangerous cause.

Reactive (Postprandial) Hypoglycaemia

Some people, especially those without diabetes, get hypoglycaemia a few hours after eating. The body releases too much insulin, pushing blood glucose too low. Signs show up about two to four hours after a meal. It is not fully understood why this happens, but it is more common after stomach surgery.

Factitious Hypoglycaemia

This is rare and involves people taking insulin or diabetes drugs they do not need, sometimes as self-harm, sometimes by accident. Children may be affected if they get hold of an adult’s medication.

Other Rare Causes

There are a few rare causes:

Insulinoma: A tumour in the pancreas that makes too much insulin, lowering blood glucose
Genetic Disorders: Some children are born with conditions making them unable to manage blood sugar properly

People Most at Risk

Anyone can get hypoglycaemia if enough of the causes are present. Still, some people are more likely to develop it. Being aware helps keep people safe.

People who are more at risk include:

Older adults, especially those with frailty or dementia
Children with type 1 diabetes
People with unpredictable eating patterns
People taking certain combinations of medicines
Those unable to communicate symptoms (e.g., dementia, learning disabilities)

Recognising Patterns and Contributing Factors

Recognising the causes of hypoglycaemia is not always simple. Several factors might combine. For example, an older man with diabetes may be unwell with a urine infection, eating less, taking his usual insulin, and then his carer encourages a walk. All these things added together cause hypoglycaemia.

Look for links between:

Medication doses and timing
Food intake and timings
Changes in activity
Illness, stress, or infection
Alcohol intake
New or changed medicines

Keeping records helps spot patterns. Share your observations with other health and care professionals if you spot someone at risk.

Environmental Factors

Environment can play a role too. Hot weather increases risk by raising activity and causing more rapid absorption of insulin injected into the skin. Social events may change meals, activity, or medication routines, leading to accidental low blood sugar.

Preventing Hypoglycaemia

Preventing hypoglycaemia is better than treating it. The key to prevention lies in identifying risks, raising awareness, and acting early.

You can help by:

Supporting regular mealtimes
Checking that food provided contains carbohydrates
Reminding people to carry quick-acting sugar sources, such as glucose tablets or sugary drinks
Monitoring for any illness and reporting changes to health staff
Checking medication timing and doses are correct
Encouraging routine blood glucose checks when required

You will need good communication with the person, their family, and the wider care team.

Common Signs That Suggest a Cause

Sometimes the signs of hypoglycaemia give clues about the cause. Patterns matter:

If it happens after missing a meal, suspect timing issues with food and medicines
If it happens after exercise, think about increased activity
If someone has new medicines, look for drug interactions
If it occurs with illness, check for infection or new health problems

Act on early warning signs to keep people safe.

Impact of Causes in Day-to-Day Care

Hypoglycaemia can affect a person’s confidence and independence. Repeated episodes can lead to anxiety, fear of eating, or avoidance of usual activities. People may become less willing to take medicines that are needed for their diabetes, because they fear more episodes. They might lose trust in care staff if these causes are not identified.

Safeguarding people means spotting and acting on all possible causes of hypoglycaemia in your care setting.

Practical Scenarios and Examples

Let’s look at some examples from real care settings.

Example 1: Missed Breakfast

Mary is an 82-year-old woman with type 2 diabetes. She usually eats breakfast at 8am, but the carer was delayed until 9.30am. Mary had already taken her diabetes tablets. At 9am, she began sweating and feeling shaky. Her blood sugar was 2.7 mmol/L. This episode was caused by delay in eating after taking her medicine.

Example 2: Extra Activity Without Food

Sam is a 45-year-old man with type 1 diabetes. He decided to mow the lawn without eating extra carbs. He developed hunger, confusion, and nearly passed out. The extra activity used up his blood sugar quicker than normal.

Example 3: Illness

Tracey, a woman with diabetes and kidney disease, developed a chest infection. She ate much less than normal but continued her full insulin dose. She soon developed hypoglycaemia, caused by less food, illness, and her kidneys not clearing insulin from her blood.

Example 4: Alcohol

Gemma, age 22, went out drinking with friends. She had not eaten all day. Later, at home, she fell unconscious. The alcohol stopped her liver from releasing stored sugar, causing hypoglycaemia.

Supporting People at Risk

Support works best when it is personal. Ask about any changes to routine, appetite, or activity. Liaise with pharmacists or diabetes nurses if medicines change. Give information and reassurance to people and their families.

Encourage open reporting if someone feels “not quite right” or if missed meals happen. Involve other professionals if hypoglycaemia happens more than once.

Final Thoughts

Identifying the causes of hypoglycaemia is vital for protecting the wellbeing and independence of anyone in your care. Every person is different, but medication, diet, illness, activity, and alcohol are the main factors you need to think about each day. By staying alert to changes, acting early, and communicating clearly, you make a huge difference.

Hypoglycaemia is frightening but often avoidable. Build routines that fit each individual and stay flexible to changes. Give people the information and tools to manage their own risk where safe. Support and teamwork help prevent problems before they start, keeping everyone in your care as safe as possible.