Why we don't offer continuous glucose monitors (CGMs)

We've looked closely at the evidence and decided not to offer CGMs to people without diabetes. Our doctors assess every test we sell against the same bar: does it give you accurate information, and does it lead to something you can act on? As things stand, we believe that CGMs don't meet this.

That isn't a verdict on the technology. For people with diabetes, CGMs are genuinely life-changing, and they've replaced several finger pricks a day.

But what does continuous glucose data give someone whose glucose regulation works normally? We explain how they work, what they can tell you, and alternative tests you might want to try instead.

How a continuous glucose monitor (CGM) works

A CGM uses a small filament sitting just under your skin to measure glucose in the interstitial fluid around your cells, rather than in your blood itself. It samples continuously and sends a reading to your phone every few minutes.

Your glucose naturally rises and falls all day in response to meals, exercise, stress, and sleep. A rise triggers your pancreas to release insulin, which works like a conductor opening doors so glucose can move into your muscles and liver.

More data doesn't always mean better decisions

We like data! But data you can't interpret doesn't turn into insight: it turns into noise, and noise around food can be really costly.

The most common way people use a CGM is to find out which foods spike their blood sugar, then avoid those foods. That sounds sensible, but it can make you optimise around the wrong things. A flat glucose line isn't the same as a healthy, nutritious, and well rounded diet.

For example, an apple raises your blood sugar. It also gives you fibre, vitamin C, and potassium. If you judge meals on the graph alone, you can be nudged away from really healthy and downright enjoyable foods.

This can also cost you time. Real-time feedback on everything you eat can tip into anxiety about eating, particularly for anyone with a history of disordered eating or restriction.

There are no agreed benchmarks for people without diabetes

Many people enjoy more data, and for this reason, the CGM is appealing. But what are you looking for?

There's no settled answer to what a "good" CGM reading looks like if you don't have diabetes, so there's nothing reliable to compare your numbers against.

In practice, people fill that gap with the thresholds they can find, which are the ones written for diabetes. Dietitian Dr Nicola Guess has described CGM use in people without diabetes, explaining that there is little evidence on benchmarks we can really trust.

This, in itself, can be pretty dangerous. An unremarkable post-meal reading can look alarming against a benchmark that isn't really a benchmark.

When researchers asked clinicians to interpret CGM reports from people without diabetes, they didn't consistently agree with each other either.

This is changing, slowly. A 2023 analysis of CGM data from more than 7,000 adults without diabetes proposed the first reference values for this group, which is the groundwork future research needs. However, it isn't yet a basis for telling you what your own readings mean.

A CGM can't catch pre-diabetes early

One of the strongest selling points is early warning. The idea is that if you wear a CGM, spot trouble coming, you can act before it becomes type 2 diabetes.

However, the data from a CGM isn't the best way to identify your type 2 diabetes risk.

The beta-cell changes and insulin resistance that come before type 2 diabetes develop well before glucose readings shift noticeably. By the time your glucose looks off, the process is already happening.

There's early work on whether CGM patterns might help flag cardiovascular risk. While this is exciting, it's still in its earlier stages.

CGM readings might be unreliable

A 2025 randomised crossover trial compared CGM readings against finger-prick capillary blood, the practical reference standard, in 15 healthy adults.

The CGM read about 0.9 mmol/L higher both fasting and after meals, and the size of that gap varied by person and by food.

It's a small study, and accuracy is improving with each generation of sensor. But it points at a significant issue: a CGM measures interstitial fluid rather than blood, which introduces a margin of error.

Where a CGM is useful

Used for a short, structured period, a CGM can help you build awareness of how your own body responds to food.

However, there are caveats here. This is best done with a qualified healthcare professional who can help you understand what the numbers mean. It's also likely not a good idea for people with a history of eating disorders or restrictive eating behaviours.

If you're experiencing difficulty with disordered eating, please explore resources from BEAT, the eating disorder charity.

What we test instead

If you want to understand your metabolic health, a few markers can give you more useful information. They include:

• HbA1c: your average blood sugar over roughly three months. It's how diabetes is actually diagnosed, and it's a strong predictor of cardiovascular disease.
• Lipid profile: triglycerides, LDL cholesterol, and HDL cholesterol. The triglyceride to HDL ratio is a useful surrogate marker for insulin resistance.
• High-sensitivity CRP (hs-CRP): a marker of low-grade inflammation, which tracks with insulin resistance.

These come back with reference ranges built from large populations, which means a doctor can tell you what your result means and what to do next.

Learn about your metabolic health with a Thriva home blood test →

What actually affects your metabolic health

You don't need to watch every glucose fluctuation to be metabolically healthy. These are the things with the strongest evidence behind them.

• Weight and waist circumference: in the Diabetes Prevention Program, a lifestyle programme built around a 7% weight-loss target and 150 minutes of activity a week cut the incidence of type 2 diabetes by 58% over about three years in people at high risk.
• Your overall dietary pattern, not individual spikes: closer adherence to a Mediterranean pattern is associated with lower rates of type 2 diabetes, and diet quality overall is one of the clearest levers you have. More whole grains, fruit and veg, legumes, nuts, and olive oil.
• Daily movement: regular activity improves insulin sensitivity and builds muscle, which gives your body somewhere to put glucose (walks count!).

The takeaway

We don't offer CGMs for people without diabetes because the data is hard to interpret, easy to misread, and doesn't answer the question most people buy one to answer. A short, supported period of use to build awareness is a fair experiment. Indefinite tracking isn't.

The markers we do offer, HbA1c, lipids, and inflammation, come with the context that makes a number mean something.

Disclaimer: This information is for general educational purposes only and isn't a substitute for professional medical advice, diagnosis, or treatment. Always speak with a qualified healthcare professional first if you have concerns about your health.