What is a blood sugar spike?
A "blood sugar spike" is an everyday term for blood sugar (glucose) rising sharply after a meal and then dropping again. It is not a formal diagnosis; the closest medical term is postprandial (after-meal) hyperglycemia. It tends to happen when you eat a lot of fast-digesting carbohydrates at once, such as white rice, noodles, bread, rice cakes or sweet drinks.
Blood sugar rises after meals even in people without diabetes, but it usually returns below 140 mg/dL (7.8 mmol/L) within 2 hours. Frequent high after-meal peaks can be an early sign that insulin is not working as well as it should, which is worth paying attention to from your 40s.
What are the symptoms?
Commonly described signs include:
- Feeling very sleepy or sluggish 1–2 hours after eating
- Getting hungry again, or craving sweets, soon after a meal
- Trouble concentrating and tiredness after meals
But overeating, poor sleep and digestion can cause the same feelings, so symptoms alone cannot tell you whether you have blood sugar spikes. Only a blood test can.
What are normal blood sugar levels?
Diagnostic thresholds used by the Korean Diabetes Association are the same as those used by the American Diabetes Association.
| Test | Normal | Prediabetes | Diabetes |
|---|---|---|---|
| Fasting glucose (no food for 8+ hours) | Under 100 mg/dL (5.6 mmol/L) | 100–125 mg/dL | 126 mg/dL (7.0 mmol/L) or higher |
| 2-hour glucose (after a 75 g glucose drink) | Under 140 mg/dL (7.8 mmol/L) | 140–199 mg/dL | 200 mg/dL (11.1 mmol/L) or higher |
| HbA1c (average over 2–3 months) | Under 5.7% | 5.7–6.4% | 6.5% or higher |
After-meal glucose can rise before fasting glucose does. If diabetes runs in your family or you carry weight around your waist, ask about an HbA1c test as well.
There is no official threshold for what counts as a "blood sugar spike." In people without diabetes, after-meal glucose usually stays below 140 mg/dL, and for people with diabetes the Korean Diabetes Association's self-monitoring targets are 80–130 mg/dL before meals and under 180 mg/dL two hours after. Numbers you see online such as "dangerous above X after eating" are mostly not official diagnostic criteria, so rely on the tests in the table above.
Does changing the order you eat really help?
Eating vegetables first, then protein, and carbohydrates last has some research support.
- US study (Diabetes Care, 2015): When 11 people with type 2 diabetes ate the same meal in a different order, eating vegetables and protein first and carbs last lowered glucose at 30, 60 and 120 minutes by about 29%, 37% and 17%.
- Japanese research (reviewed in 2014): Eating vegetables before carbohydrates lowered after-meal glucose swings and peaks, and people with diabetes who kept it up long term had better glucose control.
The studies were small and mostly in people with diabetes, but the approach costs nothing and has almost no downside, so it is worth trying.
Habits that reduce spikes
1. Vegetables, then protein, then carbs
Start with a few bites of salad or cooked vegetables, then fish, tofu, eggs or meat, and finish with rice or bread. You don't need to skip the carbs, only change the order.
2. Take a light walk after meals
A 2022 meta-analysis in Sports Medicine found that breaking up long periods of sitting with light walking lowered after-meal glucose compared with sitting the whole time. A 10–15 minute stroll after eating, or simply moving around doing chores, helps. See our walking guide.
3. Cut refined carbs and sugary drinks
Swap white rice for mixed-grain rice and white bread for whole wheat. Cut liquid sugar first, such as sweetened coffee, fruit juice and soda; drinks raise blood sugar fastest.
4. Eat slowly and don't skip meals
Skipping meals and then eating a large one makes the rise bigger. Spread your food across three similar meals and eat slowly.
Do you need a continuous glucose monitor without diabetes?
More healthy people now wear continuous glucose monitors (CGMs), sensors on the arm that show glucose around the clock. CGMs are proven tools for people with diabetes, especially those using insulin. But there is not yet good evidence that they improve health in people without diabetes. Short rises after some foods are normal, so there is no need to worry over every reading.
See a doctor for testing if
- A checkup showed fasting glucose of 100 mg/dL or higher, or HbA1c of 5.7% or higher
- You are very thirsty, urinate often, or are losing weight without trying
- A parent or sibling has diabetes, or you had gestational diabetes
- If you use insulin or a sulfonylurea, watch for low blood sugar (cold sweats, shakiness, dizziness) when walking after meals.
Please keep in mind
- This article is based on information checked as of the date shown at the top. New research or changes in official guidelines may change the details, so please use it as a reference rather than taking it as definitive.
- For an accurate diagnosis and advice about your health, please see a doctor in person.