Hypoglycemia: what it is, low blood sugar and its causes

Hypoglycemia is a condition in which the blood glucose level drops below healthy values. It is most often encountered by people with diabetes who receive insulin or other glucose-lowering medications, and without diabetes it occurs rarely. Below — what the numbers in a test mean and when a doctor is needed.

What hypoglycemia is

Glucose is the main sugar in the blood and the main source of energy: it is formed from food, and insulin helps it get into the cells. In diabetes, insulin is insufficient or works less well, so glucose stays in the blood, and glucose-lowering medications reduce it — sometimes too much. Hypoglycemia means low glucose: the level falls below what is healthy for a particular person. The literature also has a formal definition — a blood glucose concentration below 3.9 mmol/L, which causes hypoglycemic syndrome to develop.

What blood glucose is considered low

Thresholds in different reference books differ slightly: different units are used — mmol/L and milligrams per deciliter.

• below 4 mmol/L — a level already considered low in people with diabetes;
• below 3.9 mmol/L — the definition of hypoglycemia in the medical literature;
• below 70 milligrams per deciliter — a reference point for many people with diabetes (MedlinePlus);
• below 55 milligrams per deciliter — a typical threshold for people without diabetes (MedlinePlus).

Symptomatic hypoglycemia is distinguished separately: symptoms are present, but sugar is normal or even elevated — this happens with a sharp drop from high numbers to usual ones. It requires medical attention, so glucose is checked before drawing conclusions from how one feels.

What to remember: a number below 4 mmol/L is a reason to investigate, and the personal target range for diabetes is determined by the treating team.

Possible causes of low blood sugar

In diabetes, the cause is usually medications: insulin and some other agents, for example gliclazide and glimepiride, lower glucose and sometimes excessively. The risk is higher if the insulin dose is more than needed, if injections are often given in the same spot, if a meal is skipped or contains few carbohydrates, if activity has increased without changing food and dose, if there is a lot of alcohol and especially on an empty stomach. Episodes of illness, when a person eats little, also add risk. Sometimes the cause cannot be established.

Without diabetes, low glucose occurs rarely. Possible causes include malnutrition, Addison's disease, a pancreatic tumor, liver and kidney diseases, deficiency of certain hormones, weight-loss surgery, and certain medications, for example some heart medications and antibiotics. The literature also mentions severe conditions: renal, hepatic, or heart failure, sepsis, wasting.

Symptoms of low sugar

Symptoms increase quickly, and they differ from person to person. The classic set: hunger, dizziness, anxiety or irritability, sweating, tremor, palpitations, confusion. On the nervous system side, reduced concentration, disorientation, impaired coordination, and drowsiness are added. In a severe state, seizures and loss of consciousness are possible.

What to remember: a combination of sweating, tremor, and confusion is a reason to check glucose immediately, without waiting for symptoms to worsen.

Why hypoglycemia is dangerous and what complications occur

The condition requires a quick response so that it does not get worse. A distinction is made between mild hypoglycemia, when the person is conscious and manages on their own, severe — when the help of others is needed, and hypoglycemic coma — loss of consciousness. Severe hypoglycemia can lead to fainting, coma, and even death.

How it is diagnosed and when to see a doctor

In diabetes, the basis of monitoring is regular self-monitoring: a glucometer or a continuous glucose monitoring system. The doctor may order laboratory tests: a glucose test, a C-peptide test, a glucagon test, and determination of insulin in the blood. If there is no diabetes and low glucose recurs, the examination is aimed at finding the cause. A reason to see a doctor is frequent episodes, severe attacks, episodes at night, and situations when a person stops recognizing symptoms. Without diabetes, consultation is needed for tremor, sweating, rapid heartbeat, and confusion.

Low glucose by itself is not a reason to call an ambulance; 103 or 112 — if, with very low sugar, the person is unconscious or responds inadequately, and also if they consumed alcohol shortly before.

The material is for reference and does not replace a doctor's consultation: the decision on examination is made by the doctor.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer