Blood glucose often rises during a COVID infection, so tighter monitoring, steady fluids, and a clear sick-day plan help you stay safer.
If you live with diabetes, getting sick can feel like someone secretly changed the rules on you. Meals get weird. Sleep gets choppy. Stress hormones climb. Even your usual doses can hit differently.
COVID is no different. It’s a respiratory virus, yet it can push blood sugar up, set off ketones in type 1 diabetes, and leave you dealing with swings for days. The goal here is simple: help you spot the patterns early and respond with a calm, repeatable plan.
This is general education, not a replacement for your clinician’s advice. If you’ve been given a personal sick-day plan, follow that first.
Why Illness Pushes Blood Sugar Up
When your body fights an infection, it releases stress hormones like cortisol and adrenaline. Those signals tell the liver to dump glucose into the bloodstream so you have fuel to respond. If you don’t make enough insulin, or your body resists insulin, that extra glucose can pile up fast.
At the same time, you may eat less, skip meals, or throw up. That can pull glucose down. So you can see both highs and lows in the same day, even if you’re doing the “right” things.
COVID can also bring fever, dehydration, and reduced activity. All three can make insulin work less well, which can nudge sugars higher.
COVID And Blood Sugar In Diabetes: What Changes During Infection
People often report that COVID days feel different from a standard cold. You might run hotter for longer. You might sleep poorly. You might lose appetite or taste. Each of those can change glucose trends.
Start by assuming you’ll need more data than usual. Your meter or CGM trend arrows are your early warning system, not a scorecard.
Common Patterns You May Notice
- Higher fasting readings from overnight stress hormones and poor sleep.
- Spiky post-meal numbers because insulin sensitivity drops.
- Unexpected lows if you aren’t eating, you’re vomiting, or you over-correct a high.
- More ketones in type 1 diabetes, sometimes even when glucose isn’t sky-high.
Start With A Simple Rule: Measure More Often
If you’re used to checking a few times a day, bump it up during acute illness. The American Diabetes Association’s sick-day guidance stresses extra monitoring and having a plan for both highs and lows during COVID illness (ADA sick-day steps for COVID illness).
If you use a CGM, glance at trends more frequently and confirm with a fingerstick if readings don’t match how you feel.
What Drives Highs During COVID
Not every high has the same cause. Naming the driver helps you pick the cleanest fix.
Fever And Dehydration
Fever increases fluid loss. Dehydration concentrates glucose in the blood and makes it harder for insulin to do its job. If you’ve got a fever, steady fluids become a priority. Sip small amounts often if your stomach is off.
Inflammation And Stress
Stress is not just mental. Your immune response changes insulin sensitivity. You may see “sticky” highs that take longer than usual to come down.
Medications, Especially Steroids
Some people with moderate to severe COVID receive corticosteroids such as dexamethasone. Steroids can raise blood sugar and increase insulin needs. A clinical review on dexamethasone in COVID talks through glucose management points during steroid treatment (Dexamethasone guidance for glucose management).
If you’re prescribed steroids, ask for a clear plan: when to check, when to adjust, and when to call in readings. Steroid-related spikes often hit later in the day, so afternoon and evening checks matter.
Table: Symptom-To-Action Map For Glucose Swings
The table below links common COVID situations to the glucose shift you may see and the first step that often helps.
| Situation | Why Glucose Shifts | First Step That Often Helps |
|---|---|---|
| Fever | Stress hormones rise; fluid loss increases | Check more often; sip fluids; follow your correction plan |
| Loss of appetite | Less carbohydrate intake; meds may outpace food | Use easy carbs if needed; avoid skipping basal insulin |
| Nausea or vomiting | Carbs don’t stay down; dehydration builds | Small sips of carb-containing fluids; check ketones if type 1 |
| Diarrhea | Fluid loss; uneven absorption | Oral rehydration; watch trend arrows and symptoms |
| Poor sleep | Cortisol rises overnight | Extra morning check; review overnight basal if you have a plan |
| Low activity | Muscles use less glucose | Light movement if safe; watch for delayed highs |
| Steroid treatment | Insulin resistance increases | Expect higher needs; track afternoon/evening readings closely |
| New cough with fast breathing | Stress response climbs; dehydration risk rises | Check glucose; monitor symptoms; seek care if breathing worsens |
Type 1 Diabetes: Ketones, DKA Risk, And When To Act
In type 1 diabetes, illness can tip you toward ketones and diabetic ketoacidosis (DKA) faster than you’d expect. DKA happens when insulin is too low for your body’s needs, so fat breakdown accelerates and ketones build up.
Some people get ketones even when glucose is not high. That can happen if you’re eating very little, vomiting, or dehydrated. The safest move is to follow your sick-day ketone plan.
NHS Scotland’s type 1 sick-day guidance lays out a clear cadence for checking glucose and ketones during illness (NHS Scotland type 1 sick-day guidance).
Red Flags That Call For Urgent Help
- Moderate or large ketones that don’t fall with your sick-day steps
- Repeated vomiting or you can’t keep fluids down
- Rapid breathing, severe fatigue, or confusion
- Severe abdominal pain
If you have these signs, treat it as urgent. DKA can progress quickly.
Type 2 Diabetes: Hyperglycemia, Dehydration, And Medication Choices
In type 2 diabetes, COVID can still push sugars high for days. Dehydration can make you feel worse and can also strain the kidneys. Your plan is still built on monitoring, fluids, and medication choices that match what you can eat and drink.
Some people temporarily need insulin during a serious infection even if they don’t use insulin day to day. That decision is for your clinical team, yet the logic is straightforward: during stress, insulin needs can rise beyond what pills can handle.
Metformin, SGLT2 Inhibitors, And Illness Days
Medication rules depend on your health history, kidney function, and how sick you are. Many clinics use “sick-day” instructions that pause some meds during dehydration or reduced intake. If you already have written instructions, keep them on hand. If you don’t, it’s worth asking your prescriber for a simple list that says what to hold and when to restart.
Table: A Practical Monitoring Rhythm While You’re Sick
This table is a plain-language way to think about checks and action points. Use your clinician’s targets if they differ.
| Check | Suggested Cadence | Action Trigger |
|---|---|---|
| Blood glucose (meter or CGM) | Every 2–4 hours while awake during acute illness | Repeated highs even with corrections or frequent lows |
| Ketones (type 1, or type 2 on SGLT2 meds) | Any time you feel unwell, plus with sustained high glucose | Moderate/large ketones or rising ketones |
| Temperature | As symptoms change | Persistent high fever or fever with dehydration signs |
| Fluids | Small sips every 10–15 minutes if tolerated | Dark urine, dizziness, dry mouth, or minimal urination |
| Food/carbs | Try small carb doses across the day if you can’t eat meals | Unable to eat for many hours with insulin on board |
| Breathing symptoms | Check in with yourself a few times per day | Shortness of breath at rest, chest pain, blue lips, confusion |
Food And Fluids When Appetite Drops
When you feel rough, perfect nutrition is not the goal. Stable intake and hydration are the goal. A few practical options can carry you through the worst day or two.
Fluids First
Choose water, broth, or sugar-free drinks when glucose is running high. If glucose is low or you can’t keep food down, carb-containing fluids can prevent a crash: juice diluted with water, oral rehydration solutions, or regular soda in small sips can work.
If you’re vomiting, tiny sips are often easier than big gulps. Set a timer and take a few mouthfuls every few minutes.
Easy Carbs That Are Gentle On The Stomach
- Toast, crackers, rice, or plain noodles
- Applesauce or bananas
- Soup with noodles or rice
- Yogurt if you tolerate it
If you’re on insulin, carbs can be your tool to match your doses while you get better. If you’re not eating, your clinician may adjust bolus doses, yet basal insulin often still needs to continue in type 1 diabetes.
When To Call Your Clinician Or Seek Care
Some situations are beyond home management. The faster you spot them, the better your odds of a smoother course.
Call Soon If You See These Patterns
- Glucose stays high for many hours and corrections aren’t working
- You’re getting repeated lows because you can’t eat
- You’re on steroids and glucose is climbing day after day
- You have ketones that persist even after your sick-day steps
Seek Urgent Care For Breathing Or DKA Signs
Shortness of breath at rest, chest pain, confusion, fainting, or signs of DKA need urgent evaluation. Don’t try to “sleep it off.”
Lowering Risk Before You Get Sick
People with diabetes are listed among conditions linked with higher risk of severe COVID outcomes on CDC guidance (CDC list of underlying conditions linked with severe COVID).
A Simple Sick-Day Kit For Diabetes
- Glucose strips or a charged CGM receiver
- Ketone strips (urine or blood) if you may need them
- Fast-acting carbs (glucose tabs, juice boxes)
- Oral rehydration solution packets
- A written list of your meds, doses, and clinician contacts
Putting It All Together: A Calm 24-Hour Plan
If you’re sick with COVID and you’re not sure what to do first, run this loop:
- Check glucose and write down the number plus trend.
- Drink fluids, then drink again 10–15 minutes later.
- Eat a small carb dose if you can’t manage a meal.
- Use your correction plan if you have one, then re-check.
- Check ketones if you have type 1 diabetes, you feel unwell, or glucose is staying high.
- Call for help early when you see red flags.
That’s it. When you’re sick, simple wins.
References & Sources
- American Diabetes Association (ADA).“If You Get Sick, Know What to Do.”Sick-day steps for monitoring, treating highs and lows, and planning during COVID illness.
- National Library of Medicine (PMC).“Dexamethasone therapy in COVID-19 patients: implications and guidance for the management of blood glucose.”Clinical overview of steroid-related hyperglycemia and glucose management points.
- NHS Scotland.“Sick Day Guidance for Type 1 Diabetes.”Practical guidance on glucose and ketone checks and actions during illness.
- Centers for Disease Control and Prevention (CDC).“Underlying Conditions and the Higher Risk for Severe COVID-19.”Lists diabetes among medical conditions linked with higher risk of severe COVID outcomes.