Hyperglycemia and hypoglycemia in type 1 diabetes

Photo of a woman with a glass of water (PantherMedia / Sven Weber) Hyperglycemia occurs when blood sugar levels are too high. People develop hyperglycemia if their diabetes is not treated properly. Hypoglycemia sets in when blood sugar levels are too low. This is usually a side effect of treatment with blood-sugar-lowering medication.

Diabetes is a metabolic disease with far-reaching health effects. In type 1 diabetes, the body only produces very little insulin, or none at all. In type 2 diabetes, not enough insulin is released into the bloodstream, or the insulin cannot be used properly.

We need insulin to live. Without it, sugar (glucose) builds up in the blood because it cannot be taken out and used by the body. Very high blood sugar, known as hyperglycemia, leads to a number of symptoms. If blood sugar levels are too low, it is called hypoglycemia.

When is blood sugar considered to be too high or too low?

Slight fluctuations in blood sugar levels are completely normal and also happen on a daily basis in people who do not have diabetes. Between around 60 and 140 milligrams of sugar per deciliter of blood (mg/dL) is considered to be healthy. This is equivalent to blood sugar concentrations between 3.3 and 7.8 mmol/L. “Millimole per liter” (mmol/L) is the international unit for measuring blood sugar. It indicates the concentration of a certain substance per liter.

If type 1 diabetes is left untreated, people’s blood sugar levels can get very high, sometimes exceeding 27.8 mmol/L (500 mg/dL). Blood sugar concentrations below 3.3 mmol/L (60 mg/dL) are considered to be too low. As you can see in the illustration below, there are no clear-cut borders between the normal range of blood sugar and high and low blood sugar. 

Illustration: Normal range of blood sugar between hyperglycemia and hypoglycemiaBlood sugar: Normal range between hyperglycemia and hypoglycemia

Signs of hyperglycemia

Signs of very high blood sugar levels in type 1 diabetes may include the following:

  • Extreme thirst, drinking a lot and then urinating frequently as a result
  • Unintentionally losing a lot of weight within a few weeks
  • Noticeable loss of energy with muscle weakness, tiredness and generally feeling quite unwell
  • Nausea and stomach ache
  • Trouble seeing
  • Poor concentration
  • Frequent infections (cystitis, thrush)
  • Confusion and drowsiness, or even coma

If you or your child have these symptoms, you should see a doctor as soon as you can.

Signs of hypoglycemia

Low blood sugar is most common in people who use insulin or take certain tablets to reduce high blood sugar. This is because things like unplanned physical activity, eating meals later than usual, or drinking too much alcohol can mean that you need less insulin than you thought, causing your blood sugar to drop very low.

Signs that your blood sugar is too low may include:

  • Racing pulse
  • Cold sweats
  • Pale face
  • Headache
  • Feeling incredibly hungry
  • Shivering, feeling weak in the knees
  • Feeling restless, nervous or anxious
  • Difficulty concentrating, confusion

These symptoms do not occur all at once. The signs of hypoglycemia not only depend on the blood sugar level, but also vary from person to person. If you are not sure whether your blood sugar is too low, you can measure it to make sure. Mild hypoglycemia doesn't usually have any harmful effects. But it is important to react quickly enough and eat or drink something, such as dextrose sugar or sugary lemonade.

People who have severe hypoglycemia may feel very drowsy and confused, and might even become unconscious. If this happens, someone else can inject the hormone glucagon. If this is not possible it is important to call the emergency services (in Germany and many other countries: 112, in the United States: 911) immediately and ask for medical help.