Can Covid Affect Blood Sugar? | When Glucose Runs High

COVID-19 can raise glucose for days, and some people also see higher readings during recovery.

COVID-19 is a respiratory illness, yet plenty of people notice it shows up on their glucose meter first. Maybe your readings climb even though you’re eating less. Maybe you don’t have diabetes and still get a surprise “high” on a routine lab. That can feel unsettling.

Here’s the plain takeaway: infection puts your body in a higher-glucose mode. That’s a normal defense response. It can still be risky if you already live with diabetes, prediabetes, or insulin resistance. It can also matter if you’re new to glucose tracking and don’t know what’s normal for you.

This article explains why COVID-19 can push blood sugar up, what patterns people tend to see, which meds can nudge readings, and how to manage “sick days” without guessing. You’ll also get a clear list of red-flag signs that call for urgent care.

What Blood Sugar Changes People Notice With Covid

Glucose changes during COVID-19 often follow a few repeatable patterns. Not everyone gets the same pattern, and some people see swings instead of a straight climb.

Higher fasting numbers

A common report is waking up with higher-than-usual readings. This can happen even if appetite is low. Overnight, your liver can release more glucose as part of the body’s stress response.

After-meal spikes that feel out of character

Some people see bigger jumps after meals they normally handle well. If your body becomes less responsive to insulin during illness, the same carbs can produce a higher peak.

More variability day to day

Day 2 might look fine, then day 3 looks wild. Fever, poor sleep, dehydration, and medication timing can all shift quickly during an acute infection.

Readings that stay elevated after symptoms calm down

Even when the fever breaks and energy starts coming back, glucose may take longer to settle. Recovery can still involve inflammation, reduced activity, and interrupted sleep, all of which can keep readings up.

Why Covid Can Push Blood Sugar Up

When your body fights an infection, it uses glucose as quick fuel. To make that fuel available, it releases stress hormones that raise blood sugar and reduce how well insulin works. It’s a built-in survival system.

Stress hormones and “insulin resistance” during illness

During infections, hormones like cortisol and adrenaline rise. They tell the liver to release stored glucose and tell muscles and fat cells to take up less glucose. The net effect is higher blood sugar for the same food and the same meds.

Inflammation can change how glucose is handled

Inflammation affects signaling in many tissues, including those involved in insulin action. For people with type 2 diabetes or prediabetes, that can stack on top of existing insulin resistance.

Dehydration concentrates glucose

Fever, rapid breathing, sweating, and not drinking enough can lead to dehydration. Less fluid in circulation can make glucose readings look higher. Dehydration also raises the risk of ketones in people who use insulin.

Activity drops, sleep gets messy

When you’re sick, you move less. That alone can raise glucose. Poor sleep can also increase insulin resistance the next day, even if you barely ate.

Steroids and some treatments can raise glucose

Some COVID-19 cases involve corticosteroids or other treatments that nudge blood sugar up. Steroids are known for raising glucose, sometimes sharply, especially later in the day.

Can Covid Affect Blood Sugar?

Yes, it can. COVID-19 can raise blood sugar through the same “sick day” pathways seen with other infections, and the swings can be larger if you already have diabetes or insulin resistance.

Even people without a prior diabetes diagnosis can see temporary hyperglycemia during illness. In some cases, a COVID-19 infection is followed by a new diabetes diagnosis, which is why follow-up with your clinician after recovery can be worthwhile if your numbers stayed high or symptoms persisted.

Who Is More Likely To See A Spike

Anyone can see higher glucose during illness. The odds and the size of the change tend to be higher in a few groups.

People with type 1 diabetes

Illness can raise glucose and ketones quickly, even when food intake is low. For many people with type 1, ketone checks are part of the sick-day routine, since diabetic ketoacidosis can develop faster than you’d expect.

People with type 2 diabetes or prediabetes

If insulin resistance is already in the picture, stress hormones can push glucose higher with less “buffer.” Some people also take meds that must be handled carefully during dehydration or poor intake.

People with obesity, metabolic syndrome, or a history of gestational diabetes

These conditions can signal underlying insulin resistance. COVID-19 can add more insulin resistance on top of that, so the meter may climb sooner.

People taking steroids

Steroid-related hyperglycemia can be pronounced. If you were prescribed steroids for breathing symptoms or another condition during the same period, plan for closer monitoring.

Older adults and people with multiple medical conditions

Risk factors for severe COVID-19 overlap with risk factors for glucose dysregulation. The CDC’s overview of medical conditions linked with higher COVID-19 risk can help you gauge your baseline risk profile. CDC guidance on conditions linked with higher COVID-19 risk.

What High Blood Sugar During Covid Can Feel Like

Some people feel nothing and only notice the number. Others get clues from the body. These symptoms can overlap with COVID-19 symptoms, which is why a meter or CGM can be useful during illness.

• More thirst than usual
• Dry mouth
• Needing to pee more often
• Blurry vision
• Headache or fatigue that feels “different” from the fever fatigue
• Nausea or stomach discomfort

If you use insulin, add ketone checks to the plan when glucose stays high or you feel progressively worse. Ketones plus illness can escalate quickly.

How To Track Glucose During Illness Without Guessing

The goal during illness is fewer surprises. That means more frequent checks, steady fluids, and clear rules for when to seek medical care.

Use a check schedule you can stick to

If you normally check once or twice a day, illness is not the time for “business as usual.” A simple approach is to check every 4 hours while awake, then tighten to every 2–3 hours if numbers are climbing, you’re vomiting, or you’ve started steroids.

For a practical baseline, the CDC’s sick-day page lays out a straightforward cadence and basic steps like staying hydrated and continuing diabetes meds unless your clinician told you otherwise. CDC sick-day steps for diabetes.

Log a few details that explain the number

You don’t need a long diary. A short note next to a high reading can save time later:

• Temperature or fever status
• Meal timing and rough carbs
• Hydration (normal, low, vomiting, diarrhea)
• Any new meds (especially steroids)
• Ketone result if you checked

Watch for “stacking” effects late in the day

Steroids, poor sleep, and reduced activity can combine to push glucose higher in the afternoon and evening. If you’re seeing a consistent pattern, share that pattern with your clinician so dosing changes can be made with real data.

Common Covid-Related Triggers That Raise Glucose

The list below helps you identify what’s driving the spike, since the fix depends on the cause. Use it as a fast scanner when a number surprises you.

Trigger	Why glucose rises	What helps
Fever	Higher stress-hormone output and more liver glucose release	More frequent checks, fluids, med plan per clinician
Dehydration	Less circulating fluid can concentrate glucose	Small, steady sips; oral rehydration if tolerated
Reduced appetite	Less food can still pair with higher liver output	Carb intake spread out; avoid skipping basal insulin
Vomiting or diarrhea	Fluid loss plus difficulty keeping carbs down	Ketone checks, rapid action if worsening symptoms
Poor sleep	Next-day insulin resistance can increase	Rest blocks, gentle pacing, glucose checks on waking
Steroids	Direct glucose-raising effect, often later in the day	Extra monitoring; clinician-directed dose changes
Less movement	Lower muscle glucose uptake	Light walking when safe; avoid strenuous effort if ketones
Stress and pain	Adrenaline and cortisol increase glucose availability	Breathing drills, hydration, steady meals if tolerated

Medication Notes During Covid

If you take diabetes medication, illness is the time to follow a written sick-day plan when you have one. If you don’t have one, start with conservative rules and loop in your clinician early, especially if you’re vomiting, dehydrated, or seeing ketones.

Insulin users

Many clinicians advise continuing basal insulin even if you’re eating less, since illness can push glucose up. Rapid-acting insulin needs can change quickly based on food intake and steroid timing. Ketone checks become a bigger part of the routine when glucose stays elevated.

Oral meds and non-insulin injectables

Some medications can be tricky during dehydration or poor intake. The action depends on your specific prescription list, kidney function, and symptom severity. A short call to your clinic can prevent mistakes, especially if you can’t keep fluids down.

The American Diabetes Association provides a patient-friendly sick-day planning sheet that many people print and keep with their supplies. ADA sick-day planning sheet (PDF).

COVID-19 treatment and glucose

Some treatments used in moderate or severe illness, especially steroids, can raise glucose. If a hospital team starts steroids, ask what monitoring plan they want you to follow after discharge and what number should trigger a call.

After Recovery: When To Recheck Labs

If you don’t have diabetes and you saw elevated readings during COVID-19, it’s reasonable to recheck after you’ve recovered and your routine is back. Many clinicians use A1C and fasting glucose as follow-up markers. If you already have diabetes, a post-illness review can help reset your routine and confirm whether medication changes made during illness should be reversed.

Some research has found higher rates of newly diagnosed diabetes after SARS-CoV-2 infection in certain groups, including children and adolescents in specific analyses. That’s not a guarantee for any one person, yet it’s a good reason to take persistent symptoms and sustained high readings seriously. CDC MMWR report on diabetes diagnoses after SARS-CoV-2 infection.

Practical Steps That Usually Lower Glucose During Covid

These steps are simple on paper and harder when you feel lousy. Keep them small and steady.

Hydrate in a way your stomach tolerates

If nausea is present, go with frequent small sips rather than large glasses. If you’re sweating or running a fever, fluid needs rise. If you have kidney or heart issues that limit fluids, follow your clinician’s limits.

Keep carbs consistent when you can eat

When appetite is low, it’s tempting to skip meals. That can backfire if you take insulin or meds that can cause lows. Aim for small carb portions spread across the day. Think toast, soup with crackers, yogurt, rice, or fruit, based on what stays down.

Stick to a monitoring rhythm

A rhythm beats perfect timing. If checking every 4 hours is realistic, do that. If you use a CGM, confirm unexpected readings with a fingerstick when symptoms don’t match the sensor.

Use your “call thresholds” early

Don’t wait until you’re depleted. If your glucose is rising and you can’t keep fluids down, call earlier than you think you need to. Fast action prevents ER-level problems.

When To Get Urgent Care

Use this table as a quick safety screen. If you’re unsure, err on the side of getting medical help. For insulin users, ketones plus rising glucose can turn serious quickly.

What you notice	What it may suggest	What to do now
Persistent vomiting or you can’t keep fluids down	Dehydration and rising ketone risk	Call urgent care or your clinician same day
Moderate or high ketones (blood or urine) with illness	Risk of diabetic ketoacidosis	Seek urgent medical evaluation
Rapid breathing, shortness of breath, or chest pain	Severe COVID-19 symptoms or metabolic imbalance	Emergency services
Confusion, severe drowsiness, or fainting	Severe dehydration, very high glucose, or other complication	Emergency services
Glucose stays very high despite your usual correction steps	Illness-driven insulin resistance or steroid effect	Call your clinician for a same-day plan
Signs of severe dehydration (dry mouth, dizziness, very dark urine)	Low fluid volume raising glucose and strain on kidneys	Urgent care, especially if worsening

How To Prepare Before You Get Sick Again

Even if you’re reading this while sick, you can still set up a better plan for next time once you feel steadier.

Build a simple sick-day kit

• Extra test strips or CGM sensors
• Ketone strips or a blood ketone meter (if you use insulin)
• Thermometer
• Electrolyte drinks or oral rehydration packets
• Easy carbs that sit well: crackers, soup, rice, applesauce

Write down your personal thresholds

Ask your clinician for three numbers that remove guesswork: a glucose number that triggers extra checks, a ketone threshold that triggers urgent care, and a dehydration symptom list that should prompt a call.

Plan for COVID-19 prevention too

Reducing infections reduces sick-day glucose swings. If you’re in a higher-risk group, keep up with the COVID-19 prevention steps recommended by public health sources and your clinic.