All about hypoglycaemia

Who is affected?

You need to be concerned about ‘hypos’ only if you are being treated with insulin, a sulphonylurea (SU) or glitinide tablets. If your diabetes is controlled just by diet or you are taking metformin, thiazolidinediones or acarbose, you will not experience this problem.

What is hypoglycaemia?

Hypoglycaemia means low blood glucose and, in a person who doesn’t have diabetes, the levels never fall much below 3.5 millimoles per litre (mmol/l). This is because their natural control system will sense the drop, and correct the situation by stopping insulin secretion and releasing other hormones such as glucagon, which boost blood glucose. What’s more, the person will start to feel hungry, and so do the right thing by eating, so raising the blood glucose.
When you’re on insulin or SUs, this feedback system no longer operates. Once you have taken insulin or stimulated its production with tablets, you can’t switch it off again, so your blood glucose will go on dropping until you have some food in the form of carbohydrate.
As the level falls, it usually triggers a variety of warning symptoms (see box on page 77). Hypoglycaemia is dangerous because the brain depends almost entirely on glucose for normal functioning. If levels drop too low, it starts to work less well and produces the symptoms shown in the box. If the level drops even lower, unconsciousness (coma) may result.

Symptoms of hypoglycaemia

You should be aware of the symptoms of hypoglycaemia, so that you can take appropriate action. Frequent ‘hypos’ may indicate that your treatment or eating pattern needs adjusting.

• Feeling sweaty or cold and clammy

• Trembling and feeling weak

• Tingling around your lips

• Feeling hungry

• Blurred vision

• Feeling irritable, upset or angry

• Unable to concentrate

• Looking pale

• Feeling drowsy (and losing consciousness if nothing is done)

Sometimes, people with low blood glucose levels may behave oddly, so that others may suspect them of being drunk.
Most people who are taking insulin can use their symptoms as a signal that they need to have some food fairly quickly.
However, just which symptoms you get and how severe they are is an individual thing – some people feel hungry before noticing anything else; others experience tingling round the lips or shakiness, for example.
You may not experience all of these symptoms, but it is usual to have a headache after a ‘hypo’.
Reaction times may be prolonged for several hours after experiencing a hypoglycaemic reaction. Patients should not drive or undertake hazardous activities during this time.

Preventing hypos

In past years, someone who was being started on insulin might have had to go through a deliberately induced hypoglycaemic reaction so that he or she would know how it felt. These days your doctor is unlikely to suggest this because it’s not very pleasant!
Doing a blood glucose test yourself means that you can find out quickly and easily whether your level is getting too low and take action if necessary.
One of the most important aspects of caring for patients with diabetes is trying to ensure that they don’t suffer from hypoglycaemic reactions. This involves the individual concerned discussing treatment and adjusting it if necessary to fit in with his or her lifestyle, especially with mealtimes and work patterns.
This is not always easy, and sometimes it means compromises will have to be worked out.
You usually have to accept that there is no alternative to sticking to regular mealtimes, however inconvenient you find it. With the wide range of different insulins and types of injection device, it is
usually possible, however, to arrive at a treatment programme that will suit you.
Having regular hypoglycaemic attacks is a sign that you need to go back to your doctor or nurse to see how your treatment and/or eating pattern can be adjusted to prevent them happening.

What causes hypos?

You’ll soon get to recognise the situations where you are especially vulnerable, but the most common are:

• Eating later than you had expected or planned, which is bound to happen sometimes. If you’ve had your insulin injection and then can’t eat for some reason, you should eat a small carbohydrate snack (such as a boiled sweet or a biscuit), which you ought to have handy at all times.

• A burst of unexpected exercise – such as running for a bus (for more on this, see page 86).

• Drinking too much alcohol. When your liver has to break down excessive quantities of alcohol, it can’t produce glucose at the same time. This is why you’ll be advised not to drink too much alcohol if you’re on insulin or taking SUs or glitinides. Always eat something whenever you do have an alcoholic drink.

Treating a hypo

A reaction that’s relatively mild can usually be dealt with quite simply – a glass of Lucozade or lemonade should do the trick. Remember, however, that diet drinks contain artificial sweetener rather than sugar, so are of no use to you in this situation.
Do make sure, too, that, wherever you are, you always carry some sort of readily available carbohydrate in the form of a boiled sweet or biscuit.
Chocolate is not very useful in this situation because it is a slow-release form of carbohydrate. Having readily available carbohydrate is especially important if you’re a driver or if you’re about to take some form of vigorous exercise. For more on this, see the sections on diet (page 18) and exercise (page 86).

Severe hypos

Very occasionally, you may find that your blood glucose level drops so rapidly that you don’t have time to take the corrective action described above. You may become drowsy or unconscious, and might even have an epileptic fit.
This is obviously a frightening prospect both for you and for those close to you, and you need to take action to make sure that it doesn’t happen again. This means getting advice from your medical team to get the problem sorted out. There are various ways of dealing with a person who’s having a severe hypo:

• When you’re not in a state to eat or drink anything, a sugary gel called Glucogel or Hypostop can be squirted into your mouth or rubbed on your gums. This should not be done if you are having a fit.

• A hormone called glucagon, which causes blood glucose to rise, is available in injectable form. You can be given an injection into your arm or buttocks to bring you round, so you can then have something to eat or drink. Glucagon should not be used if hypoglycaemia is the result of SU or glitinide treatment, or alcohol intoxication.

Night-time hypos

It’s natural for you and your family to worry that you might have a hypo while you’re asleep, or even that you might have one and not wake up. This is an especially frightening prospect when you are the parent of a small child with type 1 diabetes – for more on this, see page 100.
In reality, the problem is by no means as dramatic as that. First, you are quite likely to be woken up by the symptoms of falling blood glucose. You may feel sweaty, restless or irritable. Occasionally, your restlessness may wake your partner even if you stay asleep.
It’s not unusual to sleep right through a severe hypoglycaemic reaction. Your body mobilises various hormones in response to the falling level of glucose, which stimulates the release of stored glucose to correct the situation. After a reaction like this, you would wake up with a headache and symptoms much like a bad hangover.
Sometimes, there may be a swing too far in the opposite direction, so that your blood glucose rises too high. If you regularly wake up feeling bad with these sort of symptoms it’s a good idea to take a few early morning (2 to 4am) blood glucose tests to see if you are having hypoglycaemic reactions that you’re not aware of at the time. At least then you’ll know why you’re feeling so bad and you can talk to your diabetes care team about whether your night-time dose of insulin needs adjusting or altering to a different type.

Losing your hypoglycaemic awareness

You may well have read various stories about some people with diabetes complaining that they have lost their ‘early warning system’ of a hypoglycaemic reaction. Many of them believe that this has happened as a result of changing from animal to human insulin. Before we consider this aspect, we should look at other reasons why this awareness might be lost.
It has become increasingly clear for some years that people who have had diabetes for a very long time become less able to predict when they are about to
have a hypo. The warning signs seem to become less noticeable after they’ve been on insulin for about 15 to 20 years. Although no one knows quite why this should be so, it is true that the ability of the pancreas to release glucagon in response to low blood glucose diminishes over time. Some people say that their symptoms change, whereas others say that the symptoms come on so much faster that they don’t have time to take corrective action.
The problem is also more common in people whose average blood glucose levels are on the low side of normal. Sometimes, adjusting the treatment so as to allow the blood glucose level to rise slightly may mean that the person gets the old pattern of symptoms back, but any change of this kind must be discussed carefully with the diabetes care team. Diabetes UK has suggested ‘four is the floor’, that is, they recommend that blood glucose levels should not be allowed to drop below 4 mmol/l.

Is human insulin to blame?

The question of what role human insulin may play in changing hypoglycaemic awareness is even more complex. Although some patients feel that changing from animal insulin is responsible for their difficulties, their doctors often disagree. Carefully controlled experiments have shown no measurable difference in hypoglycaemic symptoms in people taking animal or human insulin. All the same, some people are quite sure that they feel better on animal insulin and, if so, there is absolutely no reason why they shouldn’t go on taking it.

Can hypoglycaemia be avoided by constant high blood glucose levels?

Having persistently high blood glucose levels will avoid hypoglycaemia, but unfortunately this also increases the risk of developing complications of diabetes (see page 107).
Maintaining the balance between risky hyperglycaemia (too much) and troublesome hypoglycaemia (too little) can be very difficult for patients on insulin, but is much easier these days with the different preparations and injection devices available.
If you are having troublesome hypo attacks, followed by high blood glucose levels, consult your diabetes care team because it may mean that your treatment needs adjusting or changing. It may also be worth considering insulin pump treatment (see pages 61–2).

KEY POINTS

Hypoglycaemia can occur in any patient taking insulin or sulphonylurea (SU) tablets
Individual patients differ in their warning signs of hypoglycaemia
If you think a hypo may be coming on, try to confirm with a blood test first
If this is not possible take some fast-acting carbohydrate such as Lucozade, lemonade (not low calorie) or glucose tablets
Milk and chocolate biscuits are not ideal because they are not rapidly absorbed, but can be useful after initial correction
If hypoglycaemia is a recurrent problem, seek advice from your diabetes care team