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Topic last updated: 30 Sep 2021
    • Ico Human Biology Human biology
    • Biologybiology Biology
    • Ico Citizenship Studies PSHE / Citizenship studies
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Diabetes 16+

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Regulating blood glucose levels

Glucose is essential for all cells of the body. It provides the 'fuel' for respiration in mitochondria which generates ATP, the energy source for all cell processes. Without a sufficient supply of glucose, cells quickly start to 'shut down' processes. It is therefore important to regulate the supply of glucose in the blood. Brain cells are particularly sensitive to low glucose levels.

Blood glucose levels rise after a meal, as digested food is absorbed in the small intestine, and fall between meals as glucose is used by the cells of the body. The graph shows the fluctuations in glucose levels throughout the day in a person without type 2 diabetes and a person with type 2 diabetes.

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Graph showing the changes in blood glucose levels throughout the day.

Unregulated blood glucose

If a person with diabetes does not regulate their blood glucose, they can fluctuate between excessively high levels (hyperglycaemia) and too little (hypoglycaemia) glucose. If this situation happens over several years, both can cause problems.


  • Blood glucose above normal
  • Damage to endothelial cells lining the blood vessels.
  • Damage to capillaries in retina (blindness), kidneys and elsewhere
  • Poor peripheral circulation leading to tissue damage.
  • Heart attacks and strokes.
  • Peripheral nerve damage.
  • Damage to insulin-producing beta cells in pancreas
  • Diabetic ketoacidosis (DKA) and hyperglycaemic coma.


  • Blood glucose below normal
  • Confusion and loss of consciousness as brain cells starved of glucose.
  • Hypoglycaemic coma and possible death if not treated promptly. Treatment is to administer glucose.


Diabetic complications: Incidence / year / 1,000 persons

Complication Type 1 diabetes Type 2 diabetes
Angina 8.8 38.4
Heart attack 8.6 21.9
Stroke 1.1 14.2
Lower-limb amputation 3.2 3.1
Peripheral vascular disease 5.5 13.6
Blindness 1.1 1.6
End-stage renal disease 6.4 5
Deaths 14.6 50.0

More details of the complications caused by poorly controlled blood glucose levels


Insulin and glucagon

These two main hormones are involved in the regulation of blood glucose levels.

Insulin and glucagon regulate blood glucose levels