A blood glucose meter is an instrument used to measure blood sugar levels.

A blood glucose meter is an instrument used to measure blood sugar levels, primarily for monitoring the glycemic status of patients with diabetes. Regular use of a blood glucose meter allows individuals to closely track their blood sugar levels, enabling timely adjustments to diet and exercise to help manage the progression of the condition. As such, it is an indispensable tool for people living with diabetes.

Glucose meters are mainly classified into two types: the electrolytic method and the photochemical reaction method.

1. The electrolytic method relies on the fundamental principle of detecting the current signal generated during the reaction to quantify blood glucose. In this process, an enzyme catalyzes the oxidation of glucose, producing electrons that are counted by an ammeter; the total number of electrons is then converted into a glucose concentration reading.

2. The photochemical reaction method detects changes in the color of a small test strip during the chemical reaction to indicate blood glucose levels. Based on the intermediate products formed by the enzymatic reaction between the enzyme and glucose, a detector measures the intensity of light reflected from the test strip’s surface and converts this reflected-light intensity into a glucose concentration.

Why is blood glucose monitoring prohibited? When performing precise measurements, the following aspects should be taken into account:

1. Blood glucose measurements taken at different times are not comparable. It is recommended to measure blood glucose at home, or when comparing data, to do so at the same time each day whenever possible.

2. It is affected by factors such as insomnia and mood swings. Blood glucose levels measured under these conditions do not accurately reflect the patient’s true glycemic status; therefore, treatment should address the underlying cause rather than relying solely on glucose‑lowering medications.

3. Improper use of disinfectants can lead to inaccurate results: using povidone‑iodine or alcohol for disinfection—especially the latter, which may react with the test strip and produce falsely elevated readings. Therefore, when drawing blood, 75% medical‑grade ethanol should be used for disinfection, and testing should only proceed after the ethanol has completely dried.

4. If the blood‑collection method is incorrect, a reduced blood volume during testing may result in an unsuccessful assay or slightly lower results; in such cases, replace the test strip and retest. Additionally, if the blood spot is too large and overflows into the test zone, this can also affect the test outcome. When collecting fingerstick blood, ensure the needle penetration is adequate to avoid squeezing the fingertip.

5. The code was not set before testing. Before testing, verify that the glucometer’s code matches the code printed on the test strip packaging.

1. What is the error margin of the glucose meter?

Because glucometers still exhibit relatively significant measurement errors, the relevant regulations issued by authoritative bodies are fairly flexible. According to the national industry standard GB/T 19634-2005 for glucometers, promulgated by the General Administration of Quality Supervision, Inspection and Quarantine of China, a glucometer is considered compliant if, in 95% of precision measurements, the resulting error falls within the limits specified below.

When the test range is ≤4.2 mmol/L, the allowable error shall not exceed ±0.83 mmol/L; when the test range exceeds 4.2 mmol/L, the allowable error shall not exceed ±20%.

2. Operating Principle of the Glucose Meter

In principle, blood glucose meters fall into two main categories: optical and electrochemical. Optical glucose meters operate similarly to CD players, featuring a photoelectric sensor. Their key advantage is a lower price; however, their primary drawback is that the sensing probe is exposed to the ambient air, making it susceptible to environmental contamination and compromising test accuracy. The allowable error margin is approximately ±0.8 mmol/L, and their service life is relatively short—typically less than two years. After this period, patients using optical‑type devices are advised to have the instrument calibrated at a service center. Hospitals generally provide routine cleaning at their outpatient clinics, whereas home‑use glucose meters require periodic maintenance and calibration by the manufacturer’s after-sales service department.