Continuous glucose monitoring (CGM) has changed how we understand blood sugar. Instead of a handful of fingerstick checks, CGMs give you a near-constant readout of your glucose levels throughout the day and night. This helps us see how food, sleep, exercise, and stress really affect your metabolism. Originally created for people with type 1 diabetes, CGMs are now being used for type 2 diabetes, prediabetes, and even prevention. For patients interested in longevity and performance, CGMs provide insights that ordinary bloodwork can’t.
Time in Range (TIR): This is the percentage of time your glucose is between 70 and 180 mg/dL. For most people, the goal is at least 70% in range. Highs and Lows:
This describes how “bouncy” your glucose is. Ideally, your graph looks fairly steady, not like a roller coaster. High variability means your body is swinging between highs and lows, which increases stress and long-term risk.
When we put CGM data together, we often look at something called the AGP. Think of it like an “average day” graph that stacks your readings on top of each other. If your daily curves line up tightly, the band is narrow — that’s good. If they spread out widely, the band is wide — meaning your glucose is inconsistent from day to day.
A healthy pattern looks steady, with only mild rises after meals and quick returns to baseline. Most readings stay between 70–140 mg/dL, and the day-to-day patterns look similar.
What it means: Strong insulin sensitivity and stable metabolism.
What to do: Keep going — your current habits are supporting long-term health.
It’s normal for glucose to rise a little after meals, but repeated large spikes (160–180 mg/dL or higher) or slow returns to baseline signal early metabolic stress.
What it means: The body is struggling to manage certain meals.
What to do: Adjust meal composition — add protein or fiber, reduce refined carbs, and consider walking after meals to help glucose normalize faster. Reduce alcohol intake.
This shows up as a sharp spike followed by a steep drop, sometimes dipping below 70 mg/dL. It often happens after high-sugar or refined-carb meals.
What it means: The pancreas released too much insulin in response to the spike.
What to do: Choose balanced meals with protein and healthy fat to slow absorption. If needed, eat smaller, more frequent meals.
If your graph looks like a roller coaster with big swings up and down, you have high variability. This often shows up in people with insulin resistance, irregular meal timing, or poor sleep.
What it means: The body is struggling to maintain balance.
What to do: Regularize meals, reduce processed carbs, improve sleep, and manage stress.
Glucose may rise unexpectedly overnight. Sometimes this comes from late dinners, alcohol, or disrupted sleep. In others, it’s due to natural hormone surges (the “dawn phenomenon”).
What it means: The body is under strain during sleep.
What to do: Avoid heavy meals or alcohol at night, keep a regular bedtime, and address stress or sleep apnea if needed.
This is when your glucose is consistently higher than it should be, even when fasting. For example, waking glucose above 100 mg/dL is a warning sign of progressing insulin resistance.
What it means: Early metabolic dysfunction.
What to do: Focus on an anti-inflammatory diet, strength training, weight loss if appropriate, and consider medications like GLP-1s when needed.
A CGM isn’t just for tracking your “good days.” It’s most valuable when you experiment and see how your body responds in real life. Here are some tips:
CGMs are powerful but not perfect. They measure glucose in interstitial fluid, which lags 5–15 minutes behind blood glucose. This can cause small mismatches during rapid changes, such as right after exercise or a meal. Other common issues include:
The key: Look for patterns over days and weeks, not single numbers. When in doubt, confirm suspicious readings with a fingerstick.
CGMs give us a window into metabolism that labs can’t. Post-meal spikes, roller-coaster variability, and creeping fasting glucose are all warning signs of insulin resistance long before diabetes develops. For my patients, CGMs are powerful teaching tools. Seeing the data helps connect choices to outcomes: how a late-night snack affects sleep and glucose, or how a walk after dinner lowers the curve. Instead of abstract advice, CGMs make lifestyle changes immediate and personal.
Continuous glucose monitoring shows us how the body handles food, sleep, stress, and activity in real time. The goal is stability: high time in range, low variability, minimal spikes, and healthy fasting levels. But remember, the value of a CGM isn’t in avoiding every spike — it’s in understanding how your body reacts and learning what works best for you. When paired with expert interpretation and personalized guidance, CGMs can turn raw numbers into actionable steps for better health and longevity.
