After age 35, anyone who is overweight should get a fasting blood glucose test; if the result is normal, repeat it every three years

Cost: A fasting blood glucose test costs just a few dozen yuan. Testing for glycated hemoglobin is a bit pricier, still only a few dozen yuan. All it takes is one blood draw at a clinic.
In plain terms: For just a few dozen yuan, a single blood test can detect prediabetes even when there are absolutely no symptoms at all. Official US screening guidelines recommend this test for anyone aged 35 to 70 who is overweight or obese. If the test comes back normal, they should repeat it every three years.
Benefit: The US Preventive Services Task Force is the official body that issues screening recommendations in the US. Its current guidance states that adults aged 35 to 70 who are overweight or obese — even with no symptoms at all — should be screened for prediabetes and type 2 diabetes. Overweight is defined as a BMI of 25 or higher, while obesity means a BMI of 30 or higher. This recommendation is rated as a Grade B. The Task Force also explicitly notes: “It is reasonable to screen adults with normal blood glucose levels for prediabetes every three years.”
Evidence grade: A
Sources:US Preventive Services Task Force (2021). Screening for Prediabetes and Type 2 Diabetes. https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/screening-for-prediabetes-and-type-2-diabetes：「at a lower BMI (≥23) if the patient is Asian American」；国家卫生健康委办公厅 (2024). 居民体重管理核心知识（2024 年版）释义：「根据《成年人体重判定》（WS/T 428-2013）行业标准……24.0≤BMI＜28.0 为超重，BMI≥28.0 为肥胖」. https://www.gov.cn/zhengce/zhengceku/202407/P020240703481519509521.pdf
Notes: Having a prediabetes diagnosis does not mean you must start taking medication right away. Many people can fully reverse this condition simply by making lifestyle changes. In China, only a small fraction of adults are aware they have diabetes; most only find out after developing complications.