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Symptoms of low blood sugar

There are individual differences in the symptoms of low blood sugar and the blood sugar levels at which they occur. Low blood sugar symptoms are also called hypoglycaemia symptoms.

Symptoms of low blood sugar include, among others, feeling hungry, sweating, weakness and trembling, blurred vision, absent-mindedness, and paleness.

When the blood sugar drops too low, the body reacts, trying to return the blood sugar level back to normal. Many of the body’s glands activate and release hormones into the blood, which try to raise the blood sugar level in different ways, primarily by releasing sugar stored in the liver. Of these antagonistic hormones, the most important ones are glucagon, which is released by the pancreatic islets, as well as adrenalin and cortisol, which are released by the adrenal gland.

The symptoms resulting from adrenalin begin first. The neurological symptoms do not normally start until the blood sugar level has dropped a little bit more. During sleep, the symptoms of hypoglycaemia include restlessness, sweating and nightmares. If your blood sugar was low during the night, it may manifest as a fluctuating morning blood sugar.

Most commonly, the symptoms of low blood sugar occur when blood sugar drops below the hypoglycemic threshold of 4 mmol/l. However, these sensations are individual and influenced by various factors. For instance, the general balance of blood sugar management and the rate at which blood sugar decreases affect the symptoms of low blood sugar. If blood sugar level has been consistently high for a long time, even a blood sugar level of 4–5 mmol/l can trigger symptoms of low blood sugar. On the other hand, if blood sugar level is generally low, the symptoms of low blood sugar may be weakened or disappear entirely.

The symptoms of low blood sugar can also change over the years. The initial feelings related to adrenaline (i.e. insulin sensations) may diminish, and neurological symptoms that typically emerge more slowly may be the first sign of low blood sugar.

Symptoms caused by adrenaline are called insulin sensations. Normally, they start when blood sugar has dropped to 3.3–3.5 mol/l. The symptoms go away in 10–15 minutes, after you consume quickly absorbed carbohydrates. Normal symptoms include:

  • Shakiness, shaking hands

  • Nervousness

  • Heart palpitations

  • Cold sweat

  • Paleness

  • A strong feeling of hunger

  • Trembling

When the nervous system does not receive enough sugar, it causes symptoms. They may be the result of a lack of sugar in the local peripheral nerves or the brain. Normally, they start when blood sugar has dropped to 2.5–2.8 mmol/l. Neurological symptoms include:

  • Tiredness, fatigue

  • Trouble concentrating, confusion

  • Headaches

  • Numbness

  • Drowsiness

  • Dizziness

  • Abnormal behaviour or irritability

  • Blurred vision, seeing double

  • Seizures

  • Unconsciousness

If your blood sugar level is constantly high, your body “gets used to” it. Then, when your blood sugar level drops to normal levels, your body may think that your blood sugar is too low and you may get symptoms of low blood sugar, even if your blood sugar level is actually safely over 4 mmol/l.

In that kind of a situation, the blood sugar level is slowly and cautiously lowered. For instance, if your blood sugar has been constantly over 10 mmol/l before a meal, the pre-meal target level can be initially set at 8–10 mmol/l and later lowered to 6–8 mmol/l. The most important thing is to individually establish goals that ensure the safe correction of blood sugar levels.

Updated 8.11.2023