How is blood sugar measured?

Photo of someone pricking their finger

Many people with diabetes measure their blood sugar levels themselves. For those who inject insulin several times a day, checking their sugar levels is an important part of their daily treatment.

If someone has diabetes, their blood sugar levels are checked regularly. In type 2 diabetes, once every few months is sometimes enough. But not if insulin injections are part of their treatment. This is because the amount of insulin that is injected at mealtimes depends on the measured blood sugar level, among other things. Blood sugar levels can be measured in various ways. It is also possible to measure the level of sugar in tissues of the body.

You can learn how to measure your blood sugar yourself in special patient education classes. These are a part of diabetes disease management programs (DMPs) too.

How can you measure blood sugar yourself?

You can measure your blood sugar levels yourself using an electronic device called a blood glucose meter. To do this, you prick your fingertip with a small needle, and place a drop of blood on a test strip. The strip is inserted into the blood glucose meter. Shortly after, your blood sugar level is displayed on the device's screen.

More specifically, the procedure involves the following steps:

  • First of all, lay out everything you need. This includes a blood glucose meter, a blood-sampling device with a fine needle (lancet), and a test strip.
  • Wash your hands before measuring your blood sugar because dirt can change the results.
  • Take a test strip out of the package and insert it into the glucose meter.
  • Gently prick the tip of a finger with the needle. It hurts less if you prick the side of the finger. Gently squeeze the tip of the finger until a small drop of blood comes out. It should just fill the test field on the strip.
  • Then carefully place the drop of blood on the test strip without smearing it.
  • After a short while your blood sugar level will be displayed on the meter. Modern devices can save the measurements along with the date and time, and this information can be transferred to a computer or smartphone. If that’s not possible, it's a good idea to write the measurements down in a special diary or app, for instance.

If you measure your blood sugar levels frequently, pricking yourself is less uncomfortable if you use a different finger – or a different place on your finger – each time.

It can be helpful to read up about the various available devices and how to use them properly before getting a new glucose meter. It must be easy to use in everyday life.

What does the reading mean?

It is completely normal for blood sugar levels to go up and down a little. This also happens in people who don't have diabetes. The amount of sugar in your blood is influenced by things like what you eat and drink, how much exercise you get, and what medications you take. Depending on whether blood sugar levels are measured on an empty stomach or immediately after a meal, they vary between 3.3 and 7.8 millimoles per liter (mmol/l) in people who don't have diabetes. That’s about 60 and 140 milligrams per deciliter (mg/dl). There are no clear-cut boundaries between the normal range of blood sugar and high or low blood sugar.

Illustration: Blood sugar: Normal level between hyperglycemia and hypoglycemia, as described in the article

How is sugar measured in body tissue?

You can also monitor your sugar levels using a device that measures the amount of sugar in fat tissue underneath your skin. This approach is called continuous glucose monitoring (CGM).

A CGM system is made up of a sensor, a transmitter and a receiver (a monitoring device or an app on your phone). The transmitter is placed on the skin of your belly or upper arm using a sticky patch. The thread-like sensor is inserted into fat tissue just under your skin (subcutaneous fat) using a special insertion device. It is attached to a small transmitter that sends the measured sugar levels to the receiver, where the data is saved and can be shown on a screen.

CGM devices measure the sugar levels every few minutes, and alert you if your blood sugar is too high or too low. They are also available in combination with an insulin pump. But people with type 2 diabetes generally only use them if it’s not possible to monitor their blood sugar properly using other approaches.

When is blood sugar measured in a laboratory?

Blood sugar levels can be measured more accurately by taking a blood sample from a vein and having it tested in a laboratory. Blood sugar is often measured as part of a routine blood test in hospital or at the doctor’s. A special kind of test called a glucose tolerance test involves taking several blood samples to see how the body deals with larger amounts of sugar.

What is HbA1c?

Most people with diabetes have the HbA1c levels in their blood measured regularly. HbA1c is a measure of how high your blood sugar levels have been on average over the last two to three months. This indicates how well controlled your blood sugar is and whether your diabetes treatment might need to be adjusted.

Bundesärztekammer (BÄK), Kassenärztliche Bundesvereinigung (KBV), Arbeitsgemeinschaft der Wissenschaftlichen Medizinischen Fachgesellschaften (AWMF). Nationale Versorgungsleitlinie: Therapie des Typ-2-Diabetes. S3-Leitlinie. AWMF-Registernr.: nvl-001g. 2023.

Landgraf R, Aberle J, Birkenfeld AL et al. Therapy of Type 2 Diabetes. Exp Clin Endocrinol Diabetes 2019; 127(S 01): S73-S92.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Updated on December 18, 2023

Next planned update: 2026


Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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