A fast sugar spike does not give steady energy. It feels great when we eat it, but then our blood sugar climbs, the body quickly corrects it, and the blood sugar dip sends our levels lower than the starting point, with tiredness, brain fog and cravings that pull you back to the same high carb foods or soft drinks in a vicious cycle.
Blood sugar is not only about sweet foods. The pancreas, liver, cells, brain, gut and nervous system all take part in regulating blood sugar, and for people with histamine intolerance or mast cell reactivity, swings in blood sugar can add to the load. Below I walk through what happens in the body when blood sugar spikes and crashes, and then what helps steady blood sugar.
Do these signs of blood sugar swings sound like your day?
- A 3pm slump that arrives like clockwork
- Sugar cravings that feel louder than willpower
- Feeling wired, then tired
- Getting “hangry” between meals
- Waking at 3am
- Afternoon brain fog
- Feeling dizzy, including when you go from sitting to standing
The signs people describe are the blood sugar crash in disguise, often blamed on willpower. The rollercoaster below shows what blood sugar is doing underneath.
Making the invisible visible
What happens in your body when blood sugar spikes?
Tap any labelled part of the body to see the role each part plays in a blood sugar spike, from sugar arriving in your blood to the crash your brain feels an hour later.
Each spike of sugar sets off a chain reaction. Tap a region to follow it, one step at a time. Blood sugar isn’t just about “sweet foods”. It’s a whole-body event. See how the sugar in your blood, your pancreas, your liver, your cells and your brain all take part in the rollercoaster.
👆 Tap any labelled region to begin.
The five players in every blood sugar spike
Each part of the body has a job when blood sugar spikes. Here is the same blood sugar story as the diagram above, in plain words.
Blood glucose
When carbohydrate is eaten, digestion breaks the carbohydrate into glucose, which pours into the bloodstream. A trickle of blood sugar is clean fuel. A fast flood of carbohydrates spikes blood sugar to the top of the rollercoaster. Once blood sugar climbs, every other organ has to respond to correct it.
- Refined carbs and sugar raise blood sugar fastest
- Fibre, fat and protein slow the rise in blood sugar right down
- The higher blood sugar climbs, the harder the later drop
Pancreas and insulin
Sensing a spike in blood sugar, the pancreas releases insulin, the 'key' that opens the door to cells so glucose can leave the blood and be used or stored. A big spike in blood sugar triggers a big insulin surge.
- Insulin opens muscle and fat cells
- Insulin also tells the liver to store the excess
- An oversized surge can overshoot and drop blood sugar too low
The liver
The liver stores extra glucose as glycogen and releases glucose slowly to keep blood sugar and energy steady between meals and overnight. When blood sugar spikes are constant, the overflow keeps getting converted into fat.
- Glycogen is the liver's short-term savings account of glucose
- The liver steadies blood sugar and energy overnight and between meals
- Chronic excess is stored as body fat
Muscle and fat cells
Insulin is the key and the cell's receptor is the lock. Turn the key and glucose flows into the cell to be burned or stored. Repeated blood sugar spikes make the locks less responsive, the first step toward insulin resistance.
- Insulin is the key and the receptor is the lock
- Muscle movement helps cells pull in glucose
- Constant blood sugar spikes blunt the cells' response to insulin over time
The crash and cravings
Once the insulin surge has cleared the sugar, blood glucose can fall below the starting level, the bottom of the ride. The brain, short of steady glucose, triggers tiredness and a strong pull for more sugar. And the cycle repeats.
- An energy slump often arrives 1 to 3 hours after a blood sugar spike
- Sugar cravings are a fuel-seeking signal when blood sugar falls, not weakness
- Steady blood sugar means steadier energy, mood and focus
The core idea
The blood sugar rollercoaster, in three moves
A fast-carb meal does not give steady blood sugar. A fast-carb meal gives a climb in blood sugar, a sharp correction, and a dip that lands your blood sugar lower than where you started.
Move 1
The climb in blood sugar
Fast carbohydrate and sugar break down in minutes and flood the blood with glucose. Blood sugar shoots up and energy surges, the first hill of the ride.
Move 2
The surge of insulin
The pancreas fires out a big wave of insulin to clear sugar from the blood fast. The bigger the climb in blood sugar, the harder insulin slams the brakes.
Move 3
The crash in blood sugar
Blood sugar drops below the starting level. The brain, low on glucose, calls for more: tiredness, brain fog and cravings. So the ride starts again.
A clinical note
Blood sugar swings and your mast cells
“When blood sugar drops, the nervous system treats the drop as an emergency and releases adrenaline and cortisol to bring glucose back up. Stress signals can make mast cells release histamine, and mast cells that are already trigger happy respond faster. In clinic I have noticed that steadier blood sugar gives the nervous system, the gut and the mast cells less to react to.”
Luanne Hopkinson, Clinical Nutritionist and Nervous System Coach
Dizziness is another sign people don't connect with blood sugar. When blood sugar drops, the nervous system treats the drop as an emergency and releases adrenaline, which can leave you light-headed or shaky. Going from sitting to standing asks the nervous system to tighten your blood vessels in seconds, and skipped meals and stress hormones can make that response less steady. Dizziness has plenty of other causes too, so if the dizziness is new or severe, or you faint, get the dizziness checked by your doctor.
What shapes the ride
What steepens and what smooths your blood sugar rollercoaster
Foods that spike blood sugar fastest
Refined carbs with little fibre are digested fast, so the sugar floods into your blood and blood sugar shoots up to the top of the rollercoaster. You don't need to stop eating refined carbs, but give refined carbs some company. Protein, fat or fibre eaten at the same time slows down how fast the carbohydrate is absorbed in your gut, so blood sugar climbs more gently.
What flattens the blood sugar curve
Protein, fibre, healthy fats and a walk after a meal slow down how fast glucose gets into your blood, so blood sugar climbs more gently and doesn't crash as hard.
Signs of a blood sugar crash
The signs of a blood sugar crash are easy to blame on willpower, but willpower isn't the problem.
What helps
Ways to regulate your blood sugar
Small, repeatable habits flatten the first hill of the blood sugar rollercoaster. No habit below asks for a banned food list.
1
Start the meal with protein and vegetables
Eating protein and fibre-rich vegetables before the starchy food slows how fast glucose reaches the bloodstream. The same meal then produces a gentler climb in blood sugar.
Slow down the absorption of the carbohydrates in your gut by eating protein and fibre as well.
2
Give every carbohydrate some company
Carbohydrate eaten alone digests quickly. Fibre, fat and protein slow digestion, so glucose enters the blood gradually instead of all at once.
You don't need to stop eating carbs, but give the carbs some company.
3
Walk after eating
Ten to fifteen minutes of gentle movement after a meal sends working muscles to the bloodstream for glucose. Walking after meals is linked with a smaller rise in blood sugar.
A short walk after dinner is sociable, fun and good for your blood sugar.
4
Eat regular meals
Long gaps and skipped meals leave blood sugar low and cravings loud, which makes a fast-carb choice more likely at the next meal. Regular meals with protein keep glucose arriving steadily.
If you regularly skip meals, skipping meals might be increasing your symptoms.
5
Protect your sleep
A short night raises stress hormones and makes cells less responsive to insulin the next day. Tired brains also ask louder for quick sugar, which sends blood sugar up fast.
A tired body asks for fast fuel.
6
Settle your stress response
Stress hormones tell the liver to release stored glucose, even with no food eaten. A nervous system stuck in stress mode keeps sending glucose into the blood. Slow breathing, time outdoors and regular pauses help the nervous system settle back toward rest.
Stress alone can lift blood sugar. It's not always about what you eat.
The blood sugar habits above are general education, not personal advice. Anyone with diabetes, or taking glucose-lowering medication, needs to check dietary changes with a doctor first.
The gut connection
Your gut and your blood sugar talk to each other
Your pancreas isn't the only organ that manages blood sugar. Your gut bacteria influence blood sugar too, and your nervous system carries the messages about blood sugar between your gut and your brain.
Fibre feeds the helpers
Gut bacteria ferment fibre into short-chain fatty acids. Short-chain fatty acids can prompt cells in the gut lining to release GLP-1, a hormone that supports insulin release and slows how fast the stomach empties (Tolhurst et al., Diabetes, 2012).
The vagus nerve relays the news
Gut hormones and the vagus nerve carry information about incoming food up to the brain. The brain then adjusts appetite and insulin release in response, so the gut and the nervous system work as one loop.
Every gut responds differently
In a study of 800 people, the same food produced very different blood sugar responses from person to person, and gut microbiome makeup helped predict the difference (Zeevi et al., Cell, 2015).
Much of the research on short-chain fatty acids and GLP-1 comes from lab and animal studies, and human responses vary. Gut bacteria are one piece of blood sugar balance alongside food, sleep, movement and stress, and none of the pieces replaces individual assessment.
Sources: Zeevi et al., Cell, 2015; Tolhurst et al., Diabetes, 2012.
Frequently asked questions about blood sugar and histamine
Can blood sugar swings make histamine symptoms worse?
When blood sugar drops, the nervous system treats the drop as an emergency and releases adrenaline and cortisol to bring glucose back up. Stress signals can make mast cells release histamine, and mast cells that are already trigger happy respond faster. In clinic I have noticed that steadier blood sugar gives the nervous system, the gut and the mast cells less to react to.
Why do I crash a couple of hours after eating?
You crash because a fast-carbohydrate meal lifts your blood sugar quickly, your pancreas answers with a big wave of insulin, and your blood sugar then falls lower than where it started. A fast-carbohydrate meal can lift blood sugar within about 15 to 30 minutes. Your brain, short of steady glucose, calls for more, and that shows up as tiredness, brain fog and cravings. The energy slump often arrives one to three hours after the blood sugar spike.
Do I need to cut out carbohydrates to steady my blood sugar?
No, you don't need to cut out carbohydrates to steady your blood sugar. Give the carbs some company instead. Protein, fat or fibre eaten with carbohydrate slows how fast glucose reaches your blood, so blood sugar climbs more gently. Starting a meal with protein and vegetables, walking after eating and eating regular meals all help steady blood sugar, and no food needs to be banned.
How does the gut affect blood sugar?
Your gut bacteria affect blood sugar by fermenting fibre into short-chain fatty acids, which can prompt cells in the gut lining to release GLP-1, a hormone that supports insulin release (Tolhurst et al., Diabetes, 2012). The vagus nerve also carries messages about incoming food from your gut to your brain, and your brain adjusts appetite and insulin release in response. In a study of 800 people, the same food produced very different blood sugar responses from person to person, and gut microbiome makeup helped predict the difference (Zeevi et al., Cell, 2015). Much of the short-chain fatty acid research comes from lab and animal studies, so I see the gut as one piece of blood sugar balance alongside food, sleep, movement and stress.
Can stress raise my blood sugar even when I have not eaten?
Yes, stress can raise your blood sugar even when you haven't eaten. Stress hormones tell your liver to release stored glucose, so blood sugar can rise with no food involved. When your nervous system is stuck in stress mode, your liver keeps sending glucose into your blood, so slow breathing, time outdoors and regular pauses can help settle both your stress response and your blood sugar.
Is the blood sugar advice on this page suitable if I have diabetes?
The blood sugar habits on this page are general education, not personal advice. If you have diabetes or take glucose-lowering medication, please check any change to how you eat with your doctor first.
Keep reading
More on blood sugar, the gut and the nervous system
Blood sugar and the nervous system work as a pair
Blood sugar swings and the stress response feed each other. BrainFood is my self-paced program for working with the nervous system, with somatic exercises, breathwork, vagus nerve tools and brain retraining.
See BrainFoodReferences
- Zeevi, D., Korem, T., Zmora, N., Israeli, D., Rothschild, D., Weinberger, A., et al. (2015). Personalized nutrition by prediction of glycemic responses. Cell, 163(5), 1079-1094. https://doi.org/10.1016/j.cell.2015.11.001
- Tolhurst, G., Heffron, H., Lam, Y. S., Parker, H. E., Habib, A. M., Diakogiannaki, E., et al. (2012). Short-chain fatty acids stimulate glucagon-like peptide-1 secretion via the G-protein-coupled receptor FFAR2. Diabetes, 61(2), 364-371. https://doi.org/10.2337/db11-1019
Thriving Practitioners · Blood Sugar & the Insulin Response, a practitioner-led patient education tool
For general education only. The blood sugar timings and figures on this page are approximate teaching values, not diagnostic thresholds. The blood sugar visual aid does not replace individual assessment, diagnosis, or the management of diabetes or any medical condition.
