Normal blood sugar levels chart
Most people only see their blood sugar once a year, if that: a fasting glucose number on a blood test. It comes back "normal" and everyone moves on. The problem is that "normal" on a fasting test doesn't tell you what happens after meals, during sleep, or under stress. Those patterns matter, and they vary more than most people realise.
Fasting blood sugar (before eating)
| Category | mmol/L | mg/dL |
|---|---|---|
| Normal | 3.9 – 5.5 | 70 – 99 |
| Prediabetes | 5.6 – 6.9 | 100 – 125 |
| Diabetes | 7.0 or above | 126 or above |
After eating (1-2 hours post-meal)
| Timing | Typical non-diabetic range |
|---|---|
| 1 hour after eating | Below 10 mmol/L (180 mg/dL) |
| 2 hours after eating | Below 7.8 mmol/L (140 mg/dL) |
| Back to baseline | Usually within 2-3 hours |
HbA1c (average over 2-3 months)
| Category | HbA1c |
|---|---|
| Normal | Below 42 mmol/mol (6.0%) |
| Prediabetes | 42 – 47 mmol/mol (6.0 – 6.4%) |
| Diabetes | 48 mmol/mol (6.5%) or above |
Why "normal" doesn't mean "optimal"
These ranges define where clinical concern begins. They don't tell you how well your metabolism is functioning day to day. A person with a fasting glucose of 5.4 mmol/L is technically normal, but if their glucose spikes to 11 mmol/L after every meal and crashes to 3.5 before lunch, their metabolic experience is very different from someone whose glucose barely moves.
The blood test captures a still photograph. What actually matters is the film: the peaks, the crashes, the speed of recovery, the overnight stability. That's glucose variability, and it's the metric that correlates most closely with energy levels, cravings, weight regulation and long-term metabolic health.
What a blood sugar spike actually feels like
A glucose spike above roughly 8-9 mmol/L after eating triggers an insulin response proportional to the spike. Insulin drives glucose into cells, but if the spike was sharp, insulin often overshoots, pulling blood sugar below your baseline. That dip is the crash: the 3pm slump, the sudden hunger an hour after lunch, the brain fog that lifts when you eat something sweet.
The crash triggers cortisol and adrenaline, which signal your brain to seek fast energy. Hence the craving for sugar or carbs. The cycle repeats: spike, crash, crave, spike. Most people experience this several times a day without connecting the symptoms to their blood sugar.
What causes blood sugar spikes in non-diabetic people
Only carbohydrates break down into glucose. Proteins become amino acids; fats become fatty acids. So the primary driver of a glucose spike is the type, quantity and context of the carbohydrates in a meal.
Context matters as much as content. The same bowl of rice produces a very different glucose response depending on whether you eat it alone or after vegetables and protein. Eating fibre and protein first slows gastric emptying, which flattens the glucose curve. A 20-minute walk after eating has a similar effect: working muscles absorb incoming glucose before it accumulates in the bloodstream.
Individual variation is large. Two people eating the same meal will produce different glucose responses based on their gut microbiome, insulin sensitivity, sleep quality the night before, stress levels and dozens of other factors. Glycemic index tables give you an average; your body gives you a specific answer.
How to see your own blood sugar patterns
A continuous glucose monitor (CGM) reads your interstitial glucose every few minutes, producing a rolling graph of your metabolic response to food, sleep, exercise and stress. Originally developed for people with diabetes, CGMs are now available to anyone who wants to understand how their body processes energy.
Wearing a CGM for even two weeks reveals patterns that blood tests miss entirely: which breakfasts keep you stable until lunch, which dinners disrupt your sleep, whether your 3pm crash is caused by lunch or by the cortisol cycle. The data is specific to your body, not borrowed from a population average.
Nico pairs a CGM with AI coaching that reads your glucose data and guides you through habit changes based on what it sees. Rather than following a generic chart, you build a personalised picture of what normal blood sugar levels look like for you, and what moves them.
Ready to see what your metabolism is actually doing?