Blood sugar, insulin and HbA1c

If someone has type 2 diabetes, what is happening in their body? Type 2 diabetes means that your body is not able to use insulin effectively and it gradually stops making enough insulin. Insulin is needed to absorb sugar from the blood, and without enough insulin blood sugar levels will rise, which can be harmful to your health. 

The role of insulin

Insulin is a hormone that is released by your pancreas when you eat. The job of insulin is to help the body to absorb sugar from the meal, out of the blood and into the cells. The cells can then use the sugar for energy.

In simple terms, when your insulin levels go up, your blood sugar levels go down. When your insulin levels go down, or you cannot use it properly, blood sugar levels go up.

In people who have type 2 diabetes, either the pancreas has stopped making insulin, or the body is not responding to the signal. This means that they may need help from medication to keep their blood sugar normal. Tablets can help the body use the insulin more effectively, reduce the amount of sugar absorbed, or produce more insulin, but only while it is still making some itself. Eventually, most people will need to add insulin injections to lower their blood sugar levels.

Why is high blood sugar dangerous?

High blood sugar (also known as hyperglycaemia) damages the blood vessels. This means that vital organs and nerves may not get a sufficient blood supply, which is vital to deliver nutrients and oxygen. High blood sugar levels over a long period of time can therefore result in damage to the organs and nerves. 

Controlling your blood sugar levels will help you avoid complications like:

Heart attack 


Reduced eye sight, blindness

Kidney disease

Nerve problems

Blocked circulation in the feet


Leg amputations

Low blood sugar

High blood sugar is dangerous in the long-term. However, it’s also possible for blood sugar levels to drop too low. You may have experienced this – the faint, shaky feeling you get if you haven’t eaten for a long time. 

The medical term for low blood sugar is hypoglycaemia. People with diabetes who are on medication need to be aware of the signs of hypoglycaemia, or “a hypo”, because sometimes medication meant to lower the blood sugar (particularly insulin injections) can make it drop too low.

The signs of hypoglycaemia are:

Shakiness or feeling weak

Sweating, chills and clamminess


Rapid/fast heartbeat

Light-headed or dizziness

Nervousness, anxiety or irritability

If you have a hypo, you should treat it by consuming
15 grams of a simple sugar, like orange juice, regular fizzy drink, sweets or glucose tablets, otherwise your blood sugar could continue to drop and you may lose consciousness. As time goes on, you’ll become more familiar with what high and low blood sugar feels like, and what to do about it.

Learn more about hypos


HbA1c is a measure of blood sugar (glucose) levels. Your doctor will perform a blood test to measure your HbA1c, and it will tell them what your average blood sugar levels have been over the past
2–3 months.

A normal “healthy” HbA1c range, and that of someone with diabetes, is shown on the right:

For most people living with diabetes, the HbA1c target range is ≤7.0% and for some it is ≤6.5%. Generally, your diabetes treatment will aim to keep your blood sugar levels within a safe range, as close to normal as possible to achieve your target. However, everyone is different so your doctor will give you your own personal HbA1c goal that is safest for you. Every 1% drop in HbA1c reduces the risk of diabetes complications.

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