Diabetes: Recognizing the signs of high blood sugar

Diabetes is a metabolic disorder that has far-reaching effects on your health. In type 1 diabetes, the body cannot produce insulin. In type 2 diabetes, not enough insulin is released into the bloodstream, or the insulin cannot be used properly.

What is high blood sugar (hyperglycemia)?

It is completely normal for our blood sugar levels to go up and down a little during the day. This also happens in healthy people every day. In healthy people, blood sugar levels stay between about 60 and 140 milligram per deciliter (mg/dL) blood (3.3 to 7.8 mmol/L). Millimoles per liter (mmol/L) is a unit of measurement that indicates the amount of particles per liter and depends on the weight of the individual particles. Very high blood sugar levels, which can be higher than 27.8 mmol/L (500 mg/dL), are typical of untreated type 1 diabetes. As you can see on the graphic below, there are no clear-cut borders between the normal range of blood sugar and high and low blood sugar. To read more about the signs of low blood sugar click here.

Type 2 diabetes

Many people who have type 2 diabetes are not aware of it over years because they may not have any noticeable symptoms for a long time. The symptoms are often non-specific and could be signs of different illnesses. Sometimes complications may have already started to arise by the time type 2 diabetes is diagnosed. This form of diabetes usually starts after the age of 50. However, the number of younger people and children with type 2 diabetes has increased in recent years.

Signs of very high blood sugar levels in type 2 diabetes may include:

• general feeling of being unwell
• reduced physical fitness
• tiredness and poor concentration
• going to the toilet more often and feeling thirsty
• frequent infections (urinary tract infections, fungal infections)
• itching, particularly in the genital area
• poorly healing wounds, including small wounds
• problems seeing

Generally speaking, people are more likely to develop type 2 diabetes if they are overweight and do not get much exercise. It also sometimes runs in families, which means that people who have close relatives with type 2 diabetes are more likely to develop it too.

Type 1 diabetes

Unlike with type 2 diabetes, there is no link between type 1 diabetes and being overweight. Type 1 diabetes usually starts before people reach the age of 20. The symptoms are similar to the symptoms of type 2 diabetes, but they usually start more suddenly and are more severe.

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

• going to the toilet a lot more and feeling extremely thirsty, drinking several liters of fluid per day
• unintentionally losing a lot of weight within a few weeks
• noticeable loss of physical fitness, along with muscle weakness, tiredness and feeling very unwell
• nausea and stomach ache
• problems seeing
• poor concentration
• impaired consciousness, up to and including coma
• frequent infections (urinary tract infections, fungal infections)

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

You can read more about this topic here.

Author: Institute for Quality and Efficiency in Health Care (IQWiG)

© IQWiG (Institute for Quality and Efficiency in Health Care) Last update of this website: 05/11/2012