Yes, a cold can increase blood sugar because illness stress hormones make your body less sensitive to insulin, especially if you have diabetes.
If you live with diabetes, a sniffle can feel like more than a nuisance. You might check your meter and see numbers you rarely see on ordinary days, which adds to the tiredness and cough.
The question “Can A Cold Increase Blood Sugar?” comes up every winter in clinics and online groups. The short answer is yes, but the reasons and action steps matter just as much. Here you will learn what happens inside your body and how to keep readings steadier during a cold.
Can A Cold Increase Blood Sugar? How The Stress Response Works
When a virus hits, your immune system goes straight into defence mode. To fuel that response, your body releases hormones such as cortisol, adrenaline, and glucagon. These hormones tell your liver to release extra glucose so white blood cells and other tissues have quick energy to fight the infection.
Those same hormones also make your cells less responsive to insulin. The usual amount of insulin no longer moves glucose into cells as well as it did a few days earlier, so extra glucose from the liver pushes blood sugar higher than usual.
The American Diabetes Association notes that colds and flu can raise blood glucose and make control tougher on sick days. People with diabetes are not more likely to catch a cold, yet they often have more trouble keeping readings in range while they are ill.
| Illness Trigger | What The Body Does | Effect On Blood Sugar |
|---|---|---|
| Stress hormones | Release cortisol, adrenaline, and glucagon | Liver releases more glucose into the bloodstream |
| Inflammation | Immune cells signal for extra energy supply | Higher demand leads to raised glucose production |
| Insulin resistance | Cells do not respond as well to insulin | Same insulin dose lowers glucose less than usual |
| Fever | Body temperature rises to fight infection | Faster metabolism can push sugars up and down |
| Poor appetite | You eat less regular food or skip meals | Glucose may swing low, then climb with sugary drinks |
| Dehydration | Less fluid in the bloodstream | Glucose becomes more concentrated, readings climb |
| Cold medicines | Syrups, decongestants, and pain relief | Some products contain sugar or can raise glucose |
That mix of extra glucose, weaker insulin effect, and shifting food intake explains why readings can jump during a cold. Two people with the same virus can see different numbers, because diabetes type, usual control, kidney function, and current treatment all shape the pattern.
Cold And Flu Illnesses And High Blood Sugar Risks
Doctors and diabetes teams warn about sick days because spikes in blood sugar can tip over into emergencies. Long periods of high readings and lack of insulin in type 1 diabetes can lead to diabetic ketoacidosis. In type 2 diabetes, severe illness can contribute to hyperosmolar hyperglycaemic state, which also needs urgent hospital care.
Groups such as American Diabetes Association sick day advice explain that infections, including common colds, raise hormones that oppose insulin and push glucose up. The same message appears in guidance from Diabetes UK and national health services around the world.
For someone without diabetes, this spike is usually mild and short lived, and the pancreas simply releases more insulin for a few days. For someone who already has trouble producing or using insulin, the extra pressure from a cold can drive readings well above target.
Differences For Type 1, Type 2, And No Diabetes
Type 1 Diabetes
In type 1 diabetes, the pancreas no longer makes enough insulin. During a cold, the body still releases stress hormones and extra glucose, yet there is no natural insulin boost to match the rise. Without careful adjustment of injected insulin, high readings can turn into ketones, dehydration, and diabetic ketoacidosis.
This is why sick day plans for type 1 usually advise checking blood sugar more often, testing for ketones when readings stay high, and never skipping basal insulin even if you are vomiting. Fast access to care for severe nausea, abdominal pain, rapid breathing, or confusion can save your life.
Type 2 Diabetes
In type 2 diabetes, the body still makes insulin, but the cells do not respond well, a state known as insulin resistance. Illness hormones push resistance even further. Oral medicines or injected insulin may need temporary adjustment during a cold to handle that extra resistance.
Some people with type 2 diabetes already live close to dehydration or kidney strain. A high fever, poor intake of fluids, and raised glucose can drive them toward hyperosmolar hyperglycaemic state, with symptoms such as extreme thirst, passing large amounts of urine, weakness, and drowsiness.
No Diabetes Diagnosis Yet
Even people without a known diagnosis can see higher readings on a lab test while they are ill. Infection can reveal prediabetes or early type 2, so anyone told they had high glucose during a hospital stay or urgent care visit should arrange repeat testing once they recover.
Anyone told they had high glucose during a hospital stay or urgent care visit should arrange repeat testing once they recover. That repeat test helps separate temporary illness effects from ongoing diabetes or prediabetes.
Monitoring Blood Sugar During A Cold
When cold related spikes turn into real numbers on your meter, a clear action plan helps you stay calm. Extra checks give you real data instead of guesswork.
Many diabetes teams suggest checking every four hours while awake during mild illness, and more often for type 1 diabetes or if numbers climb quickly. Continuous glucose monitors often reveal spikes after cough syrup, snacks, or steroid nose sprays, so good records of readings, medicines, and food help you and your healthcare team agree short term changes.
Good records help you and your healthcare team decide on short term changes. Write down readings, insulin doses or tablets, temperature, and what you eat or drink. Patterns often stand out over a day or two.
| Blood Sugar Pattern | What It May Show | Typical Next Step |
|---|---|---|
| Higher all day but under your emergency level | Illness stress with partial insulin resistance | Follow your sick day rules, increase fluids, adjust doses if advised |
| High mainly overnight and on waking | Hormone surges and less activity overnight | Talk about basal changes with your diabetes team |
| Big spikes after cough syrup or cold drinks | Added sugar or certain medicines | Switch to sugar free options after checking labels or pharmacy advice |
| Wide swings from low to high | Irregular meals and vomiting | Use sick day meal ideas, contact urgent care if you cannot keep fluids down |
| Steady rise above your usual safe limit | Growing insulin lack or severe infection | Follow emergency instructions from your clinic or local services |
Food, Fluids, And Staying Out Of Trouble
Fruit juices, honey drinks, and regular sodas feel soothing during a cold, yet they pour large amounts of fast sugar into the bloodstream. Health agencies suggest small, frequent portions of easy foods such as broths, yoghurt, soft fruit, toast, or rice, along with drinks that combine some carbohydrate with plenty of water.
Plain water, sugar free squash, or unsweetened tea help fight dehydration, which otherwise concentrates glucose in the bloodstream. National health bodies also stress that people with diabetes should not stop their usual glucose lowering medicine unless a doctor or nurse tells them to do so for safety reasons.
Cold Medicines And Blood Sugar Spikes
Over the counter cold remedies can change readings as much as the virus. Thick syrups often contain sugar or honey. Decongestants that include pseudoephedrine may raise blood pressure and glucose in some people.
Before buying a remedy, read the ingredients list with care. Many pharmacies stock sugar free cough syrups and lozenges that suit people who watch their glucose more closely. If you already take medicines for blood pressure, heart disease, or kidney problems, ask the pharmacist which cold products fit your full list.
The CDC flu guidance for people with diabetes reminds readers to check with their healthcare team before taking new over the counter tablets. That advice applies to simple colds as well.
When To Call A Doctor About Blood Sugar And A Cold
Most colds fade within a week or so, and raised glucose settles down soon after. Some warning signs mean you need medical help the same day.
Contact your diabetes clinic, out of hours line, or local emergency service without delay if any of these happen during a cold:
- Repeated meter readings at or above the level your team marked as an emergency value
- Moderate or large ketones in blood or urine, especially with nausea or stomach pain
- Fast breathing, fruity breath, or deep tiredness that does not match a simple cold
- Signs of dehydration such as a dry mouth, dizziness when standing, or passing small amounts of urine
- Fever that lasts more than a couple of days or returns after starting to settle
- Cough, chest pain, or shortness of breath that feels worse than a routine cold
- Any concern that you cannot manage food, fluids, or medicines at home
Children, older adults, pregnant people, and anyone with other long term conditions should have a lower threshold for seeking help. Their bodies have less reserve, so a cold plus high glucose can turn into something serious much faster.
Everyday Habits That Lower The Odds Of Spikes
You cannot avoid every cold virus, yet steady habits can make sick days less chaotic. Flu vaccines, up to date COVID shots where advised, hand washing, and staying away from people who are clearly unwell all lower your odds of heavy infections.
Year round, stable glucose before you fall ill also gives you more buffer. That means taking medicines as prescribed, moving your body regularly, keeping regular meals instead of snacks, and staying on top of sleep, stress, and check ups.
Can A Cold Increase Blood Sugar? Yes. With a sick day plan, regular tracking, and early contact with your diabetes team, you can move through most colds without losing control of your diabetes goals.