What a CGM is, who it's for, how to read your graph, and the common mistakes I see first-timers make.
A few years ago, continuous glucose monitors were something most people only associated with Type 1 Diabetes. Today, I see them on arms at the gym, at the office and in the queue at the hawker centre.
I've worn one through my own journey of reversing Type 2 Diabetes, and I now use them with my clients. If you're curious but not sure where to start, this guide is for you.
A CGM is a small, coin-sized sensor that you wear on the back of your upper arm. A very thin, flexible filament sits just under the skin, and the sensor sends a glucose reading to an app on your phone every few minutes, 24 hours a day. Most sensors are worn for about two weeks; the Ottai sensor I use in my workshops lasts 15 days.
Instead of the single snapshot you get from a finger-prick test or an annual blood test, you get a continuous curve showing how your glucose responds to everything you do: meals, drinks, exercise, sleep, stress and even travel.
The applicator does most of the work in a second or two. Most people describe it as a quick press or a small pinch, and many forget they're wearing it within a day. If you have sensitive skin or react to adhesives, please check with your doctor before wearing one.
A CGM measures glucose in the interstitial fluid (the fluid around your cells), not directly in your blood. Glucose reaches that fluid a little later, so CGM readings can lag behind blood glucose by up to about 15 minutes, especially when levels are rising or falling quickly.1 Small differences are normal. Look at the trend rather than comparing single numbers.
Rosalind had gained 7kg during COVID. She was eating clean and exercising, and even her doctor couldn't find the problem. Her CGM revealed hidden carbs quietly spiking her blood sugar. Once she could see them, she could manage them. She lost all 7kg and more.
When you open the app, you'll see a line moving up and down through the day. Here's what I teach people to look at.
Where does your glucose sit when you haven't eaten for a few hours, such as first thing in the morning? This gives you a sense of your starting point.
It's completely normal for glucose to go up after eating. What matters is how high it goes, and how sharp the rise is.
How long does it take to come back towards your baseline? A gentle hill that settles within a couple of hours tells a very different story from a steep spike followed by a crash (often when the cravings kick in).
Your glucose overnight can reflect late dinners, alcohol, poor sleep and stress.
A multicentre study of 153 healthy people without diabetes found that glucose stayed between 3.9 and 7.8 mmol/L about 96% of the time, with an average around 5.5 mmol/L. Readings above 7.8 mmol/L added up to only around 30 minutes a day.2
Singapore uses mmol/L. Many international articles and apps use mg/dL. To convert, divide mg/dL by 18 (so 140 mg/dL is about 7.8 mmol/L). When you set up your app, choose mmol/L. In some apps, including Ottai, this can't be changed later.
The magic of a CGM is that it turns general advice into personal evidence. People can respond very differently to the same food,3 so try these and see what your body does:
Keep a quick note of what you ate and did in the app, so you can connect the dots later.
One high reading after a birthday cake isn't a problem. Look for patterns that repeat.
A healthy body's glucose moves. Cutting out whole food groups to achieve a perfectly flat graph isn't the goal and isn't sustainable.
Sleep, stress, movement and even your menstrual cycle can shift your numbers. Some of the most useful insights come from the non-food moments.
Sleeping on the arm with your sensor can press on it and cause false low readings overnight. If you see a sudden, sharp dip while you were asleep, this might be why.
A CGM is only as useful as what you do with it. Pick one or two insights and turn them into habits.
When I was diagnosed with Type 2 Diabetes at 38, my endocrinologist told me reversal was highly unlikely. My CGM became my daily teacher. It showed me which meals, habits and routines helped my body, and which didn't. Alongside changes to my diet, exercise, sleep and stress, it helped me lose 16kg and reverse my diabetes within a year.
A CGM won't change your health on its own. But it can change how you understand your health, and that understanding makes change feel less like guesswork and more like a series of small, rewarding experiments.
I'm May, a breast cancer survivor who reversed my Type 2 Diabetes with the help of a CGM. I now coach people in Singapore to understand their blood sugar and build habits that last.
Work with meJoin a CGM workshopThis article is for education only and is not medical advice. Please speak with your doctor before making major changes to your diet, exercise or medication, especially if you have a pre-existing medical condition.
