Blood glucose

How to check blood glucose at home with a meter

October 20267 min read

Whether you check your own blood glucose or your child's, a reliable reading depends on a few steps done well. Here you will find the ones described by the international guidelines for children and adolescents (ISPAD), by the US agency that authorises glucose meters (FDA), by the English health service (NHS) and by Diabetes UK: hands, finger prick, strips, testing the meter and what to write down. Every point has its source at the bottom of the page.

This guide explains how to check, not how to read the values or how to treat. What the numbers mean and what to do is set by the plan agreed with your doctor or diabetes team. If in doubt, or if you or your child are unwell, call your doctor or diabetes team.

First of all, your plan

When to check, how often and what to do with the result is decided by the diabetes team, together with you: it is your plan. The Australian diabetes service (NDSS) says it clearly: your doctor tells you when to check your blood glucose and helps you fit it into your day.

This guide is only about the act of checking. For your device, the manufacturer's instructions always apply: the FDA asks you to read them and make sure you understand them before testing.

At the beginning it is normal to have lots of questions. The English guidelines (NICE) say the team should teach you how to check and how to read the results, and that you go over these skills together at least once a year: feel free to ask to review them whenever you need.

Clean, warm, dry hands

The ISPAD guidelines list handwashing, followed by careful drying, among the conditions the accuracy of the reading depends on, together with how the blood is applied and strips that are in date and well stored.

Wash your hands with warm water and soap and dry them well before every check (CDC, FDA). If you check your child, wash their hands and yours too (Diabetes UK).
The reason is simple: traces of sugar or other carbohydrates on the fingers can make the value read higher than it really is, and water left on the skin dilutes the drop and can make it read lower (NDSS).
Do not use wet wipes: the glycerine they contain can alter the result (Diabetes UK).
Warm hands help blood reach the fingertips and make the prick less uncomfortable (Diabetes UK, NHS Leeds).
After the check, wash your hands again: the FDA recommends it to reduce the risk of passing on infections through blood.

Where to prick, and why you change finger

Use a new lancet for every check (Diabetes UK).
Prick the side of the fingertip, not the centre: it hurts less and spares the part of the finger you use most, where sore spots would otherwise form (American Diabetes Association, NHS Leeds, Diabetes UK). This applies to children too: using the side of the finger instead of the tip keeps pain to a minimum (Diabetes UK).
Change finger and spot each time: it reduces pain and helps the skin heal (NHS Leeds, Diabetes UK). Diabetes UK advises avoiding the thumb and index finger.
If the drop is small, gently massage the finger from the base towards the tip (NHS Scotland, CDC).
Throw the used lancet away in a sharps container (Diabetes UK, NHS Leeds).
Never share lancets, lancing devices or meters with anyone, not even within the family (CDC, FDA).

Some meters let you use blood from other areas, such as the palm or the forearm (FDA, American Diabetes Association). The FDA warns, however, that results from those areas can be less accurate when blood glucose is changing quickly: after a meal, after insulin or exercise, during an illness, at a stressful time, when you think you are having a hypo or when the value does not match how you feel. In these cases you check from the finger. Whether and when to use other areas, ask your team.

Strips: expiry, storage, coding

An expired or damaged strip can give a wrong value without anything flagging it (NDSS, FDA). That is why four checks are enough.

Expiry. Look at the date before using them: expired strips may not give a correct reading (NDSS, NHS Scotland). Many products also have a shelf life once the pack is opened, which varies from brand to brand (NHS North East London): you will find it in the instructions.
Storage. Keep them in their original container, tightly closed when not in use, away from moisture, heat and light (CDC, FDA, NHS Leeds, NDSS). The meter, too, should be stored as the manufacturer says (FDA): extreme temperatures and humidity can make it less accurate (ISPAD).
New strips. Always use new strips, never used or second-hand ones (FDA).
Coding. Many of today's meters code themselves: the NHS in North East London lists this among the requirements for the meters it recommends. If yours needs coding, do it as the instructions explain (FDA).

Control solution

Control solution is a liquid used instead of blood to check that the meter and strips are working properly. The Scottish health service reminds you that it is important to do this test regularly (NHS Scotland).

The FDA suggests doing the test:

every time you open a new pack of strips;
every now and then, while you are using the same pack;
if the meter has been dropped;
when a result is unusual and does not match how you feel, or how your child seems.

How to do the test is explained in the instructions for the solution and the meter. If the device is not working, the FDA advises calling the number in the manual and talking to your doctor.

What to write down, straight away

Write the value down as soon as you read it, exactly as it appears on the screen, and next to it anything that may have affected it: the CDC and the American Diabetes Association both recommend this. Put in a row, values with their context show the team a pattern that a single number cannot show (Diabetes UK, NDSS).

The date and time (NIDDK).
The moment in relation to meals: before or after a meal, at bedtime (American Diabetes Association).
The insulin taken, if your plan includes it, and what you ate, for example the carbs if you count them (American Diabetes Association, NIDDK).
The context: physical activity or sport, illness, stress (American Diabetes Association, NIDDK, NHS).
Ketones, in blood or urine, if your plan says to check them, for example on sick days (NICE). Ketone strips, too, should not be used after their expiry date (NICE).
A hypo you treated, and how you treated it following your plan: recording hypos helps to see whether they keep happening (Diabetes UK).

Write down every value, even the ones that look strange to you: Diabetes UK asks you to record them all, because together they help you and the team understand how blood glucose is behaving. If someone else sometimes does the check, for example a grandparent, show them how: the CDC recommends that another person also knows how to use the meter.

When to recheck a value

If a result seems strange to you, or does not match how you feel or how your child seems, the first thing to look at is the procedure. The Australian NDSS service suggests a few questions:

Were your hands washed and dried well?
Was there enough blood on the strip?
Are the strips out of date, or have they been exposed to moisture, heat or light?
Is the meter clean? Is it too hot or too cold? Is the battery low?

Then follow your plan: that is where the team says in which situations to repeat the check and after how long. The English guidelines (NICE) and the NHS point out that during illness and with sport more frequent checks are often needed. If you use a sensor and the value does not match your symptoms, the ISPAD guidelines advise confirming it with the meter.

If you are in doubt, or if you or your child are unwell, call your doctor or diabetes team.

The blood glucose diary, always with you

With Pediary's blood glucose diary you log by hand the values you check with your own device, in mg/dL or mmol/L, with the moment of the check, insulin, carbs, ketones and treated hypos. If your plan says to recheck, you choose when to be reminded. No colours and no judgement on the values.

Discover the blood glucose diary