Blood glucose levels
Self-monitoring of blood glucose can be a beneficial part of diabetes management. As part of the day-to-day routine it can help with necessary lifestyle and treatment choices as well as help to monitor for symptoms of hypo- or hyperglycaemia. Monitoring can also help you and your healthcare team to alter treatment which in turn can help prevent any long-term complications from developing.
Some people with diabetes (but not all) will test their blood glucose levels at home. Home blood glucose testing gives an accurate picture of your blood glucose level at the time of the test. It involves pricking the side of your finger (as opposed to the pad) with a finger-pricking device and putting a drop of blood on a testing strip.
Some people can't see the point of testing as they think they know by the way they feel, but the way you feel is not always a good or accurate guide to what is happening.
Blood glucose targets
It is important that the blood glucose levels being aimed for are as near normal as possible (that is in the range of those of a person who does not have diabetes). These are:
- 3.5–5.5mmol/l* before meals
- less than 8mmol/l, two hours after meals.
There are many different opinions about the ideal range to aim for. As this is so individual to each person, the target levels must be agreed between the person and their diabetes team.
The target blood glucose ranges below are indicated as a guide.
Children with Type 1 diabetes (NICE 2015)
- on waking and before meals: 4–7mmol/l
after meals: 5–9mmol/l.
Adults with Type 1 diabetes (NICE 2015)
- on waking: 5–7mmol/l
- before meals at other times of the day: 4–7mmol/l
- 90 minutes after meals: 5–9mmol/l.
Type 2 diabetes (NICE 2008)
- before meals: 4–7mmol/l
- two hours after meals: less than 8.5mmol/l.
Pregnant women with diabetes (NICE 2015)
fasting: below 5.3mmol/l
- 1 hour after meals: below 7.8mmol/l or
- 2 hours after meals: below 6.4mmol/l
*millimoles per litre: a measurement of the concentration of a substance in a given amount of liquid
Blood glucose meters
Choosing a meter can be quite complex as new products are coming on to the market all the time. Some manufacturers have also produced computer software packages that enable you to look at trends in your blood glucose levels. Your healthcare team should help you with choosing a meter that suits your individual needs. It's essential that you are taught how to carry out a test properly – poor technique may lead to incorrect results which could lead to inaccurate medication dosing.
- The strips used with meters are nearly always provided in batches of 50, but check with your healthcare team before choosing a meter. If you purchase testing strips from abroad or online you must check that they are calibrated to the same UK specifications.
- Meters for people with visual impairments: If you have a visual impairment that means you’re unable to use most of the meters for testing, there are some alternatives. Ask your healthcare team for advice.
- Finger-pricking devices and lancets: Finger-pricking devices are automatic devices that pierce the skin so that a drop of blood can be extracted for testing. They insert a lancet (a very short, fine needle) into the skin using a spring mechanism. The depth at which the needle is inserted can be adjusted depending on the thickness of the skin. Lancets are available in different sizes, or gauges. A higher-gauge lancet is generally less painful; however, you may not get enough blood to test with the higher-gauge needles. Lancets are designed to be used only once. If they are used more than once they become blunt and painful to use.
Worried about finger-pricking?
Many people new to life with diabetes worry about having to do blood tests. This is natural, and with help from their diabetes care team the majority of people adapt well and find it is not as bad as they feared. Anyone who is worried about doing blood tests should talk to their diabetes care team.
- There are ways to make blood glucose testing easier such as washing the hand in warm water and shaking it to increase blood flow before you test
- You should always use the sides of the fingers rather than the more sensitive fleshy pulp at the tips.
- Some blood glucose meters and lancing devices allow you to avoid the fingertips altogether and use less sensitive test sites, such as the upper arm or thigh.
Recording your results
It’s really important to record the blood tests that you do, to help you and your healthcare team to assess how well your diabetes is being managed. You might choose to record your results in a diary, use a computer software package provided by your meter manufacturer or use the Diabetes UK Tracker smartphone app. If you have Type 1 or Type 2 diabetes, or are caring for someone who does and you own an Apple or Android smartphone – you can download the free Diabetes UK Tracker app. The app is designed to be quick and simple to use, taking the daily chore out of logging levels such as blood glucose, carbohydrates and calories. The app was designed by a team that included user experience professionals, clinical specialists and people with diabetes, to help you manage your condition.
Urine testing involves holding a test strip under a stream of urine for a few seconds and comparing the colour change on the strip, after a set amount of time, with the chart on the strip container. If you have been advised to test your urine for glucose it is best to test it in the morning before your breakfast. Empty your bladder when you get up, then test a sample passed 30 minutes later. Tests done at this time should be negative. You can also test two to three hours after a meal, when your blood glucose will have been at its highest.
- Urine testing gives a less accurate picture of your blood glucose than blood testing, but your doctor may still feel that it is suitable for you. It is less accurate because there is usually no glucose in your urine unless the glucose levels have risen to 10mmol/l or above, which is considered quite high.
- Also, it does not give you an indication of what your blood glucose level is at the time you test, because the urine you are testing may have been produced several hours before you test.
- Urine tests also cannot tell you if your blood glucose is too low – which is important for people on insulin or certain tablets.
- Some people get glucose in their urine at lower levels. They are said to have a 'low renal threshold' for glucose. Older people may develop a high renal threshold, when glucose does not appear in the urine until the level in the blood is much higher than 10mmol/l. High or low renal thresholds will cause confusion if you are monitoring your diabetes with urine tests.
- Because urine testing involves comparing a colour change on the urine testing strip, it is not suitable if you are visually impaired
HbA1c (Glycated haemoglobin) and fructosamine
At least once a year, your doctor should check your long-term diabetes control by taking a blood sample from your arm.
The most common test is the HbA1c test, which indicates your blood glucose levels for the previous two to three months. The HbA1c measures the amount of glucose that is being carried by the red blood cells in the body.
For most adults with diabetes, the HbA1c target is below 48 mmol/mol, since evidence shows that this can reduce the risk of developing complications, such as nerve damage, eye disease, kidney disease and heart disease. Individuals at risk of severe hypoglycaemia should aim for an HbA1c of less than 58 mmol/mol. However, any reduction in HbA1c levels (and therefore, any improvement in control), is still considered to have beneficial effects on the onset and progression of complications.
You will now be getting used to seeing your HbA1c results reported using the IFCC (International Federation of Clinical Chemistry) reference measurement procedure of mmol/mol.
To help you with the transition from the percentage system you were used to, we have developed a converter:
Convert HbA1c % to mmol/mol and vice versa
If your red blood cells are affected by, for example, anaemia, sickle cell anaemia or thalassaemia (all of which involve a lack of or abnormal type of haemoglobin – the oxygen-carrying part) then your doctor may carry out a blood test for fructosamine. Fructosamine gives an average result for the previous 14 to 21 days. If you normally have a fructosamine test, discuss your individual target with your doctor.
Blood pressure (hypertension)
Blood pressure is a measurement of the force of blood flow inside your arteries. Your blood pressure is stated as two figures, e.g.130/80mmHg (millimetres of mercury). The first figure is known as the systolic pressure and relates to the pressure as the heart contracts and pushes blood through the arteries. The other figure is the diastolic pressure measured when the heart relaxes to refill with blood.
- For someone without diabetes the blood pressure should be no higher than 140/85 but when you have diabetes (or if you have had a heart attack, stroke or coronary heart disease) your blood pressure should be no higher than 130/80.
- It is important to have your blood pressure checked at least once a year as part of your annual review for diabetes. This helps to ensure that it is in the target range and not increasing your risk of developing diabetes complications.
Your healthcare team will help you to aim towards a target level of 130/80mmHg or less. High blood pressure usually has no signs or symptoms – occasionally people with very high blood pressure say they experience headaches – so the only way to know if you have high blood pressure is to have yours measured. High blood pressure can lead to heart attack, stroke or kidney failure. If your blood vessels are narrowed or clogged, extra strain is put on your heart as it has to work harder to pump blood around your body.
Causes of high blood pressure
For most people, there may be no single cause for their high blood pressure. It is not known exactly what causes it, but we do know that lifestyle can affect your risk of developing it. You are at a higher risk if:
- you are older
- have a family history of high blood pressure
- are of African or Caribbean origin
- eat a lot of salt
- are overweight
- do not take much exercise
- drink large amounts of alcohol
- are very stressed.
Blood fats (lipids)
Lipids are the cholesterol and triglycerides in your blood. Cholesterol is a type of fat found in all of us. You may be familiar with the term blood cholesterol, but what you may not know is that not all cholesterol is bad. Some of it, HDL (high density lipoprotein), can actually protect against heart disease. Low levels of this protective HDL cholesterol increase your risk of cardiovascular disease (CVD). However, LDL (low density lipoprotein) cholesterol is the bad form of cholesterol in the blood. It is high levels of this type that are linked with an increased risk of heart disease. Triglycerides are another type of fat in the blood. If you have raised cholesterol and raised triglycerides you have an increased risk of CVD.
- Your total cholesterol level should be below 4.0mmol/l.
- LDL levels should be less than 2.0mmol/l.
- HDL levels should be 1.0mmol/l or above in men and 1.2mmol/l or above in women.
- Triglyceride levels should be 1.7mmol/l or less.
If you do not know your lipid levels, ask your healthcare team to arrange a simple blood test for you.
Increased risk of high blood pressure: NHS Choices