COVID can push glucose up or down; tighter checks and clear sick-day steps help you stay steady and know when to get urgent care.
When you catch COVID, your glucose readings can start acting weird. That can happen even if your diabetes has been calm for months. It can even happen to people who’ve never had diabetes and never tracked glucose before.
The tricky part is that COVID doesn’t “raise blood sugar” in one simple way. The same person can run high for a couple days, dip low after a bad appetite day, spike again after a steroid dose, then settle once the fever breaks. So the goal of this page is plain: show you what changes are common, what usually drives them, and what you can do at home to stay safer.
This is general education, not personal medical care. If you use insulin, have type 1 diabetes, are pregnant, have kidney disease, or you’re seeing scary numbers, loop in your doctor’s office.
COVID Blood Sugar Levels And What Changes Mean
Glucose shifts during COVID tend to fall into a few buckets. Some come from the infection itself. Some come from dehydration and reduced food intake. Some come from meds used during treatment. The “meaning” of a change depends on the pattern, your symptoms, and whether you’re able to drink, eat, and keep meds down.
If you already use a meter or CGM, treat the first 72 hours like a higher-alert window. Check more often than you do on calm days. Log what you see with notes like fever, cough, appetite, diarrhea, and any new meds. Those notes make your numbers make sense.
If you don’t have diabetes but you’re checking glucose because a clinician suggested it after COVID, the same idea applies: patterns matter more than one reading. A single odd number can come from stress, missed meals, or dehydration. Repeated highs, paired with thirst and frequent urination, deserve a call to a medical team.
Why COVID Can Shift Glucose Readings
Stress hormones can push numbers up
Any infection can raise glucose. Your body releases stress hormones to keep fuel available for immune work. That can drive higher readings, even if you’re eating less than usual.
Less food can pull numbers down
COVID often knocks out appetite, taste, and smell. Nausea or sore throat can make meals hard. If you take insulin or certain diabetes pills, skipping carbs can lead to low glucose. That’s why “eat less” needs a plan, not guesswork.
Dehydration can make highs stick
Fever, sweating, diarrhea, and rapid breathing can drain fluids. Dehydration makes it tougher for the body to clear glucose, so highs can last longer. Hydration is not a side detail during illness; it’s part of glucose control.
Steroids can drive sharp spikes
Some people with more serious COVID get steroids like dexamethasone. Steroids often raise glucose, sometimes fast. If you start steroids, ask your care team how to adjust meds and how often to check glucose while you’re on them and for a short period after they stop.
Check More Often Without Burning Out
When you feel lousy, complicated plans fall apart. A sick-day routine needs to be simple enough to follow from bed.
Pick a schedule you can stick to
If you use insulin, more checks are usually needed. Many people do well with checks before meals, at bedtime, and once during the night while fever is active. If you don’t use insulin, you may still need extra checks if you’re seeing repeated highs, you’re dehydrated, or you’re taking steroids.
Use trend clues, not single numbers
One high reading after coughing for an hour can settle with fluids and rest. A steady climb across several checks is a different story. Write down:
- Time and reading
- Food and drinks
- Fever or chills
- Diarrhea or vomiting
- New meds, including steroids
- Any ketone results (if you check ketones)
Use device claims carefully
If you see ads for watches or rings that claim “needle-free blood sugar,” treat that as a red flag. The FDA has warned against using smartwatches or rings that claim to measure blood glucose without piercing the skin. See the FDA safety communication on noninvasive glucose claims.
Food And Fluids When You Can’t Eat Much
COVID can turn meals into a chore. Your job is to keep fluids going and get steady carbs in a form you can tolerate. Think “small and steady,” not “three big meals.”
Hydration ideas that don’t feel like work
- Water, sipped often
- Broth or clear soup
- Electrolyte drinks (watch labels if sugar is a concern)
- Ice chips or sugar-free popsicles if your throat hurts
Easy carbs for low appetite days
If you’re at risk for lows, plan on carbs you can handle. Options can include crackers, toast, applesauce, yogurt, or rice. If you’re vomiting or can’t keep food down, you may need medical care sooner, mainly if you use insulin.
When To Check Ketones
Ketones matter most for people with type 1 diabetes and for anyone who’s had diabetic ketoacidosis (DKA) before. Some people with type 2 diabetes also check ketones during illness, based on clinician advice.
Call your medical team right away if you have ketones plus rising glucose, or if you have symptoms like belly pain, repeated vomiting, deep fast breathing, or confusion. If you can’t reach a clinician and you feel worse fast, urgent care is the safer move.
What To Do With Your Diabetes Medicines During COVID
This part is personal, since meds vary. Still, a few illness patterns show up often.
Insulin users
Illness can raise insulin needs even when you eat less. That sounds backwards, yet it’s common. At the same time, low appetite can raise your risk for lows if you dose like a normal day. That mix is why sick-day plans usually include more checks and a clear set of dose rules from your clinician.
People taking pills or weekly injections
Some meds are harder to handle when you’re dehydrated or can’t keep food down. Don’t guess. Contact your prescribing team for your sick-day rules, mainly if you have vomiting, diarrhea, or poor fluid intake.
COVID care can change glucose plans
If you’re given steroids, your glucose plan may change for the steroid window. If you’re admitted to a hospital, staff may change your usual regimen to match illness needs and meal timing.
For broader guidance on illness management with diabetes, see the CDC page on Managing Sick Days. For COVID-focused diabetes notes and planning tips, the ADA has a public hub at Diabetes and Coronavirus. The International Diabetes Federation also shares practical reminders at COVID-19 and diabetes.
Common Patterns And Practical Next Steps
Use the table below as a pattern decoder. It won’t replace your clinician’s plan, yet it can help you spot what’s going on and what to do next.
| What You May Notice | What Often Drives It | What To Do Next |
|---|---|---|
| Higher fasting readings for several mornings | Illness stress hormones, poor sleep, dehydration | Increase check frequency, push fluids, follow your sick-day dosing plan |
| Big afternoon or evening spikes | Steroids, missed meds, larger “comfort meals” later in day | Ask your clinician about med timing; log steroid doses and meal times |
| Low readings after small meals | Reduced intake with usual insulin or meds | Use your low-glucose plan; add small carbs; review dosing rules with your care team |
| Numbers swing high, then low, then high again | Inconsistent eating, nausea, dehydration, changing activity | Shift to small steady carbs, sip fluids, set alarms for checks, simplify meals |
| High readings with thirst and frequent urination | Dehydration plus sustained hyperglycemia | Hydrate, recheck, contact a clinician if highs persist or you feel weak or dizzy |
| High readings plus ketones | Insulin shortage, dehydration, infection stress | Follow ketone protocol; seek urgent care if symptoms escalate |
| False “low” CGM alerts with no symptoms | Sensor compression, hydration shifts, device lag | Confirm with a fingerstick if readings don’t match how you feel |
| New high readings in someone without diabetes | Acute illness stress, steroid exposure, unmasked glucose intolerance | Repeat checks, contact a clinician if highs repeat or symptoms develop |
When Numbers Mean “Get Help Now”
Some situations call for fast action. Don’t try to tough it out when your body is waving a red flag. Seek urgent medical care if you have any of the following:
- Trouble breathing, chest pain, blue lips, fainting, or confusion
- Repeated vomiting or you can’t keep fluids down
- Signs of dehydration: severe dizziness, very dark urine, or you can’t urinate
- Ketones with rising glucose, belly pain, deep fast breathing, or fruity breath
- Severe low glucose that doesn’t respond to fast carbs, or lows that keep returning
If you’re alone, call someone to stay on the phone while you decide your next step. If your symptoms feel scary, emergency services are the right move.
How To Build A Simple Sick-Day Plan Before You Need It
The best time to set up a plan is when you’re not sick. A good plan fits on one page and answers basic questions: when to check, what to drink, how to dose meds, when to check ketones, and when to call for care.
If you already have a plan, review it once a year. Make sure supplies are in date. Put spare batteries where you can find them. Store ketone strips with your meter.
Sick-Day Checklist You Can Save
This checklist keeps the moving parts in one place. Print it or save it in a notes app. Adjust it with your clinician’s personal dosing rules.
| Checklist Item | Timing | Notes |
|---|---|---|
| Glucose check | At least before meals and bedtime | Check more often if you use insulin, have fever, or see rising trends |
| Fluids | Small sips all day | Broth, water, and electrolytes can help if you’re sweating or have diarrhea |
| Carbs if intake is low | Every few hours as tolerated | Choose easy options like toast, crackers, applesauce, or yogurt |
| Ketone check (if you’ve been told to check) | When glucose is high or you feel worse | Follow your ketone protocol; don’t delay care if symptoms stack up |
| Medication log | Each dose | Write steroid doses and times; this often explains spikes |
| Temperature and symptoms | Morning and evening | Track fever, cough, diarrhea, vomiting, and breathing changes |
| Supplies check | Day 1 of illness | Strips, lancets, sensor backups, ketone strips, fast carbs, fluids |
| Call plan | Before numbers get scary | Know who to call after hours and where you’d go for urgent care |
After You Recover: When To Keep Watching
Once COVID symptoms ease, glucose may settle right away. Sometimes it takes longer, mainly if you had a rough course, lost weight, changed meds, or had steroid treatment.
If you use a CGM, watch the trend line for a couple weeks and compare it to your pre-illness patterns. If you use fingersticks, keep a short log of fasting and one post-meal reading for several days. If you don’t have diabetes yet you saw repeated highs during COVID, ask for follow-up testing so you’re not guessing.
The main goal after recovery is simple: return to your normal routine in a steady way. Restart activity slowly if you’re still tired. Bring meals back in a way your stomach can handle. Keep hydration up. If glucose stays out of range, don’t wait it out; get a clinician involved.
References & Sources
- Centers for Disease Control and Prevention (CDC).“Managing Sick Days.”Practical sick-day steps for people living with diabetes, including monitoring and when to seek care.
- American Diabetes Association (ADA).“Diabetes and Coronavirus.”COVID-focused guidance for people with diabetes, including planning and safety tips.
- International Diabetes Federation (IDF).“COVID-19 and diabetes.”General advice for people living with diabetes during COVID, with emphasis on glucose monitoring and preparation.
- U.S. Food and Drug Administration (FDA).“Do Not Use Smartwatches or Smart Rings to Measure Blood Glucose Levels.”Safety notice warning that noninvasive watch/ring glucose claims are not authorized and may be unsafe.