Diabetes and Hypoglycemia

Hypoglycemia is defined as blood glucose levels dropping under 4 mmol/L
Hypoglycemia is defined as blood glucose levels dropping under 4 mmol/L

Hypoglycemia occurs when blood glucose levels fall below 4 mmol/L (72mg/dL).

Whilst many of us think of diabetes as being a problem of high blood sugar levels, the medication some people with diabetes take medication that can also cause their sugar levels to go too low and this can become dangerous.

What is hypoglycemia?

Hypoglycemia occurs when the level of glucose present in the blood falls below a set point:

  • Below 4 mmol/L (72mg/dL)

Being aware of the early signs of hypoglycemia will allow you to treat your low blood glucose levels quickly - in order to bring them back into the normal range.

It is also recommended to make close friends and family aware of the signs of hypoglycemia in case you fail to recognise the symptoms.

What are the symptoms of hypoglycemia?

The main symptoms associated with hypoglycemia are:

Symptoms of hypoglycemia can also include:

Who is at risk of hypos?

Whilst low blood sugar can happen to anyone, dangerously low blood sugar can occur in people who take the following medication:

If you are not sure whether your diabetes medication can cause hypos, read the patient information leaflet that comes with each of your medications or ask your doctor.

It is important to know whether your diabetes medication puts you at risk of hypos.

What are the causes of hypoglycemia?

Whilst medication is the main factor involved in hypoglycemia within people with diabetes, a number of other factors can increase the risk of hypos occurring.

Factors linked to a greater risk of hypos include:

You can take steps to minimise the risk of these factors causing hypos.


Hypoglycemia is when blood glucose levels fall below 4 mmol/L. Hypoglycemia in relation to diabetes is often abbreviated and referred to as a hypo. Hypos are more likely to occur for people taking insulin or a type of tablets called sulfonylureas.

If you’re on medication that can cause hypos, it’s important to be aware of the signs of hypoglycemia, which include:

  • feeling tired or weak
  • being hungry
  • becoming pale
  • sweating
  • becoming anxious or irritable
  • a tingling sensation in tongue or lips
  • trembling or shakiness

In more severe cases of hypoglycemia, someone with diabetes may experience:

  • confusion
  • convulsions
  • loss of consciousness

The NHS lists the following as reasons why hypos may occur:

  • If you have too much diabetes medication for the amount of carbohydrate you’ve had
  • If you miss a meal
  • If you take more exercise than normal
  • If you drink alcohol on an empty stomach

It is advisable to treat a hypo as soon as you recognise the symptoms.

Diabetes UK recommend that you treat a hypo by taking 15-20g of a short-acting carbohydrate.
Having 3 or more glucose tablets will raise your blood sugar the quickest. If glucose tablets are not available, other options can include:

  • 250ml of a non-diet soft drink
  • 250ml of fruit juice
  • Five sweets such as jelly babies

If your next meal is not due, follow the short acting carbohydrate with some longer acting carbs such as a slice or bread or a portion of fruit. It is recommended to re-test your blood sugar after 15 to 20 minutes and re-treat if your sugar levels are still less than 4 mmol/L.

If someone experiencing hypoglycemia is unconscious, the NHS advises that they are put into the recovery position and either given glucagon or an ambulance called. If no-one has been trained to give glucagon, an ambulance should be called.

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How is hypoglycemia diagnosed?

Hypoglycemia is detected by measuring blood sugar levels with a glucose meter. Any blood glucose level below 4.0 mmol/L indicates that the individual has hypoglycemia. Urine tests do not detect hypoglycemia.

If taking a blood test is not possible or would take too much time, it may be better to treat the hypo straight away.

How do I treat hypoglycemia?

A mild case of hypoglycemia can be treated through eating or drinking 15-20g of fast acting carbohydrate such as glucose tablets, sweets, sugary fizzy drinks or fruit juice.

Some people with diabetes may also need to take 15-20g of slower acting carbohydrate if the next meal is not due.

A blood test should be taken after 15-20 minutes to check whether blood glucose levels have recovered. Severe hypoglycemia may require an ambulance, for example if loss of consciousness occurs or a seizure persists for more than 5 minutes.

Severe hypos can be treated with glucagon if a glucagon injection kit is available and in date.

How serious is hypoglycemia?

Hypoglycemic episodes can range from mild to severe.

Mild hypoglycemia can usually be treated by the individual and are to be expected to some degree in people on insulin. Mild hypos are not associated with significant long term health problems unless they are occurring very regularly or for long periods of time.

Severe hypoglycemia, however, will require treatment from someone else and may require an ambulance. Severe hypos can lead to immediate danger if not treated immediately. Whilst rare, severe hypos can potentially lead to coma and death.

Do symptoms always occur before hypoglycemia?

Most people experience some warnings before the onset of hypoglycemia. However, some diabetics may experience little or no warning before the onset of sudden or severe hypoglycemia.

An impaired ability to spot the signs of hypoglycemia is known as loss of hypo awareness (or hypo unawareness).

Preventing hypoglycemia

The key to preventing hypos is understanding why hypos occur and then taking actions to stop this happening. If you know that a hypo is likely to occur soon, carbohydrate can be taken to raise sugar levels and prevent the hypo.

If your doctor is happy for you to adjust your medication doses, you can also lower your dose during or following certain activities (eg exercise or after having alcohol) to prevent a hypo occurring.

Testing blood sugar levels regularly can help you to understand when your sugar levels are dropping too low.

Your diabetes health team can help you with making changes to your diabetes management.

Are hypos catching you without warning? Join the Hypo Awareness Program for a comprehensive guide towards recovering your hypo awareness »