Blood Sugar Test for Pilots and Flying

What is the blood sugar level?

The blood sugar level is the amount of glucose (sugar) in the blood. It is also known as plasma glucose level. It is expressed as millimoles per litre (mmol/l).

Normally blood glucose levels stay within narrow limits throughout the day: 4 to 8mmol/l. But they are higher after meals and usually lowest in the morning.

In diabetes the blood sugar level moves outside these limits until treated. Even with good control of diabetes, the blood sugar level will still at times drift outside this normal range.

Why control blood sugar levels?

When very high levels of blood glucose are present for years, it leads to damage of the small blood vessels.

This in turn increases your risk of developing late-stage diabetes complications including:

retinopathy (eye disease)
nephropathy (kidney disease)
neuropathy (nerve disease)
cardiovascular disease, such as heart attack, hypertension, heart failure, stroke and problems caused by poor circulation, eg gangrene in the worst cases.

With Type 1 diabetes, these complications may start to appear 10 to 15 years after diagnosis.

They frequently appear less than 10 years after diagnosis of Type 2 diabetes, because this type of diabetes is often present for years before it is recognised.

By keeping the blood sugar level stable, you significantly reduce your risk of these complications.

How can I measure blood sugar levels?

You can learn to measure blood sugar levels simply and quickly with a home blood glucose level testing kit. All kits have at least two things: a measuring device and a strip.

To check your blood sugar level, put a small amount of blood on the strip. Now place the strip into the device. After about 30 seconds it will display the blood glucose level.

The best way to take a blood sample is by pricking your finger with a sharp lancet that's designed to penetrate the skin only as far as needed to draw a drop of blood.

What should glucose levels be?

The ideal values are:

4 to 7mmol/l before meals
less than 10mmol/l 90 minutes after a meal
around 8mmol/l at bedtime.

How often should blood glucose levels be measured?

It depends on your lifestyle - the needs of someone with diabetes who's also a PE instructor are quite different to someone who sits at a computer all day.

If you use insulin

In broad terms, people who have Type 1 diabetes should measure their blood sugar levels daily before meals. Some days one or two tests can be done, while on others four or five might be needed.

Measuring blood sugar levels in the morning before any food gives an indication of the amount of insulin needed overnight.

If you have Type 2 diabetes that's being treated with insulin, you should also follow this schedule.

If you take oral treatments

If your diabetes is treated with tablets or a special diet (Type 2), you should measure your blood glucose levels once or twice a week - either before meals or 90 minutes after a meal.

You should also do a 24-hour profile once or twice a month. This means measuring glucose levels before each meal.

Not everyone with Type 2 diabetes needs to carry out regular blood glucose checks.

For elderly people and those with other medical problems, it's often enough to check the urine for glucose - usually before breakfast and the evening meal.

This is because while good control of diabetes is important, cardiovascular complications (heart attacks, stroke, angina) are the main cause of serious illness and death in people with this type of diabetes.

So people with Type 2 diabetes will benefit from tackling the factors that contribute to their cardiovascular risk by:

controlling blood pressure more rigorously
lowering cholesterol levels with medication
increasing or starting exercise
stopping smoking.

Blood glucose levels at bedtime

The blood sugar level at bedtime should be between 7 and 10 mmol/l.

If blood glucose is very low or very high at bedtime, you may need to adjust your food intake or insulin dose. Make sure you discuss this with your doctor.

At what other times should blood glucose levels be measured?

Blood glucose should be measured any time you feel unwell or think your blood sugar level is too high or low.

If you have Type 1 diabetes and have more than 20mmol/l of glucose in your blood, you should use a urine strip to check for the presence of ketones.

One of the blood glucose meters available also allows you to check your blood for ketones.

If ketone bodies are present in your urine or blood, it's a warning sign of diabetic acidosis. If this is the case, you should consult your doctor immediately.

How is the blood sugar level checked over a period of time?

A test known as the HbA1c test can show the average blood sugar level over the previous six to eight weeks.

The test looks at levels of HbA1c in a sample of blood.

HbA1c is the compound produced by the chemical reaction between haemoglobin and glucose in the blood. HbA1c is also called glycated haemoglobin.

High blood sugar levels produce more HbA1c. But because the process happens over several weeks, an occasional blip of high blood sugar is not enough to influence the HbA1c level.

This means only consistently high glucose levels cause HbA1c levels to rise - and why HbA1c levels are used as a measure of diabetes control.

HbA1c is about 6 per cent of the total haemoglobin in people who don't have diabetes. The target to aim for is an HbA1c level of below 6.5 per cent if possible – although 7 per cent or less is very good.
HbA1c of 7.5 per cent shows only fair control of diabetes.
HbA1c above 8.5 per cent shows poor control of diabetes.

Any increase in the HbA1c level indicates poorer control of diabetes.

The United Kingdom Prospective Diabetes Study Group (UKPDS) was a 20-year-long research trial in diabetes.

It showed that for every 1 per cent rise in HbA1c, a person with Type 2 diabetes is 30 per cent more likely to develop late-stage complications arising from damage to the small blood vessels.

In Type 1 diabetes, the same relationship between high HbA1c and increased development of complications was shown by the Diabetes Control and Complications Trial in the US.

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