Why popular blood sugar monitors could actually be harming your health

Yahoo

26-02-2025

Popular glucose monitors used to take regular blood sugar readings could be driving poor diets and food restrictions due to inaccurate measurements, according to a new study.
Continuous Glucose Monitors (CGMs) take blood sugar readings every five minutes and were originally designed for people with diabetes to assess how their body responds to different foods.
But they are growing in popularity and in recent years have increasingly been used by the health-conscious to track their diet and avoid glucose spikes.
Now, research by University of Bath scientists in the American Journal of Clinical Nutrition suggests they may not be as accurate as once thought.
The study warns that monitors may be overestimating blood sugar levels in healthy adults and prompting them to make unnecessary changes to their diet.
Carried out in healthy, non-diabetic volunteers, the research compared results from a CGM to the gold standard finger-prick test for blood sugar levels.
Scientists found that the CGMs consistently reported higher levels than the finger-prick test. The monitors overestimated the time spent above the Diabetes UK's recommended blood sugar level threshold by nearly 400 per cent, causing unnecessary concern for people whose blood sugar was actually well-controlled.
Professor Javier Gonzalez, from the university's department of health, warned people should stick with the finger-prick test if they are looking for accurate readings.
'Continuous glucose monitors (CGMs) are fantastic tools for people with diabetes because even if a measurement isn't perfectly accurate, it's still better than not having a measurement at all,' he said.
'However, for someone with good glucose control, they can be misleading based on their current performance.
'For healthy individuals, relying on CGMs could lead to unnecessary food restrictions or poor dietary choices.'
While CGMs were initially designed for those with diabetes, they have been increasingly used by other health conscious people simply to track their diet and avoid glucose spikes.
After consuming a smoothie, one monitor showed a GI (Glycemic index) of 69, which is medium, while the finger-prick test showed a GI of 53, which is low.
Whole fruits, which are classified as low-GI by finger prick tests, were classified as medium or high-GI foods by CGMs.
Professor Gonzalez said CGMs may be inaccurate because they measure glucose in the fluid surrounding your cells, not directly in the blood. 'This can lead to discrepancies due to factors like time delays, blood flow, and how glucose moves between different parts of the body,' he said.
Helen Whitby, company nutritionist at Innocent Drinks, which partly funded the research, said: "Smoothies and whole fruits are packed full of natural goodness and provide steady energy without sharp blood sugar spikes.'