Diabetes sick day rules are the widely taught, general-education pillars for looking after yourself when a cold, the flu, an infection, or another illness makes managing blood sugar harder than usual. When you are sick, your body releases stress hormones that can push blood sugar higher even when you are eating less than normal — which is why a plain cold can send readings up. As general education attributed to the American Diabetes Association (ADA) and the Centers for Disease Control and Prevention (CDC), the common pillars are to check more often as your care team directs, keep drinking fluids, keep taking your medicines exactly as prescribed unless your clinician tells you otherwise, keep easy carbohydrate and fluid options on hand, and know your care team's numbers for when to call. Your personal sick-day plan, though, comes only from your own clinician — ideally written down before you ever need it.
Key takeaways
- Illness and infection trigger stress hormones (such as cortisol and adrenaline) that can raise blood sugar, which is why readings often climb when you are sick even if you eat less.
- As general education attributed to the ADA and CDC, the common sick-day pillars are checking more often as directed, staying hydrated, continuing medicines as prescribed, keeping easy carbs and fluids on hand, and knowing when to call.
- Never stop, skip, or change any medicine on your own during illness — decisions about medication always come from your care team.
- Build a personal sick-day plan with your clinician before you get sick, and call emergency services for severe symptoms such as persistent vomiting, confusion, or suspected diabetic ketoacidosis (DKA).
Short Answer: What Are Diabetes Sick Day Rules?
Diabetes sick day rules are a general framework, not a personal prescription, for staying steady when illness makes blood sugar harder to manage. In broad educational terms attributed to the ADA and CDC, they come down to a handful of habits: check more often if your care team tells you to, keep drinking fluids, keep taking your prescribed medicines unless your clinician says otherwise, keep simple carbohydrate and fluid options within reach, and know the readings and symptoms that mean it is time to call.
Those pillars are a shared starting point. The version that applies to you — how often to check, what to do about a number, your personal red flags, and who to call — is set by your care team. The most useful thing this article can do is nudge you to build that personal plan with your clinician before you are sick, so you are following a plan rather than improvising while feeling unwell.
Why Does Illness Raise Blood Sugar? (Gentle Physiology)
It surprises many people that a cold or a stomach bug can send blood sugar up even when appetite disappears. The reason is hormonal: when your body fights an illness or infection, it releases stress hormones — including cortisol and adrenaline (epinephrine) — that prompt the liver to release more glucose and make cells more resistant to insulin, so glucose builds up in the bloodstream. This is a normal response to physical stress, and pain, fever, and dehydration can add to the effect. It is also why "why is my blood sugar high when sick" is such a common question — the rise is driven by the illness itself, not by anything you did wrong.
The flip side matters too. Some illnesses, especially those with nausea, vomiting, or diarrhea, can make eating and keeping food down difficult, which for some people — particularly those on certain glucose-lowering medicines — can push blood sugar low instead. Because illness can move blood sugar in either direction, checking more often (as your care team directs) is how you find out what is happening rather than guessing. For a fuller picture of the numbers, our companion guide on what is a dangerous blood sugar level explains the general high and low thresholds and when a reading warrants urgent attention.
The Widely Taught Sick-Day Pillars (General Education)
The table below summarizes the common sick-day pillars as general education attributed to the ADA and CDC. Read each row as a shared principle, not a personal instruction — the specifics of how each applies to you come from your care team.
| Pillar (general education) | What it generally means | Who personalizes it |
|---|---|---|
| Check more often | Illness can move blood sugar up or down, so many plans call for checking more frequently than usual during sickness | Your care team sets how often and when |
| Stay hydrated | Keeping up fluids helps counter dehydration, which can accompany fever, vomiting, or high readings | Your care team advises fluid types and amounts |
| Continue medicines as prescribed | Many plans have you keep taking prescribed medicines during illness rather than stopping them | Your clinician decides any change — never do this yourself |
| Keep easy carbs and fluids on hand | Having simple options ready helps when you cannot eat a normal meal | Your care team suggests what fits your plan |
| Know your escalation numbers | Certain readings and symptoms mean it is time to call | Your care team gives you the specific numbers and contacts |
| Check ketones if directed | Some plans include checking for ketones when readings run high during illness | Your clinician tells you if, when, and how |
A few cautions belong with this table. The medicines row is the one people most often get wrong: do not stop, skip, reduce, or change any medicine on your own because you feel too unwell to eat, or because a reading looks high or low. Some medicines are continued during illness and some may be adjusted, but that decision is your clinician's. If you are unsure, that uncertainty is itself a reason to call.
Likewise, the ketones row applies to some plans and not others; whether checking ketones is part of your routine is something to confirm with your clinician. Our sibling guide on ketones in urine explains what ketones are and why they can matter during illness.
Checking More Often During Illness
Because illness can move blood sugar in either direction, more frequent checking is the thread that ties the sick-day pillars together — it turns guesswork into information you and your care team can act on, letting you catch a reading climbing toward a level that needs attention or dropping if you cannot keep food down. The exact schedule is personal, so lean on the plan your care team gives you rather than a generic rule.
For a refresher on the mechanics while you are well, our hub article on how to check your blood sugar at home walks through meter, lancet, and test-strip technique, and our guide on when to check blood sugar covers common timing patterns. Keeping a simple record during a sick spell also helps; our overview of a manual blood sugar tracking app shows easy ways to log readings you can share afterward. A single high reading during illness is expected physiology, not a verdict — the pattern over the day is what your care team uses to decide what, if anything, to do.
Fluids, Food, and Keeping Easy Options on Hand
Staying hydrated is one of the most universally taught sick-day habits, because fever, rapid breathing, vomiting, and high blood sugar can all pull fluid out of the body. General education from the CDC and ADA emphasizes keeping up fluids during illness, and your care team can tell you which fluids fit your situation and how much to aim for. Food can be harder when illness kills your appetite; the principle behind keeping "easy carbs and fluids on hand" is simple preparedness, so that if you cannot manage a normal meal you are not scrambling. What those options should be, and how they fit around your medicines, is something to sort out with your clinician before you are sick — this is educational context, not a carbohydrate prescription or a treatment plan.
If a reading runs high and you want general, non-emergency context to discuss with your care team, our article on how to lower blood sugar quickly covers approaches to bring to that conversation, and our normal blood sugar levels chart lays out typical reference ranges across the day.
When to Call Your Care Team vs. Seek Emergency Care
Knowing who to call and when is the pillar that protects you most, and it is worth settling in advance. The signs below are commonly taught as reasons to reach out — but your care team gives you your specific thresholds and contact numbers, and those personal instructions always take priority.
Reach out to your care team (per the numbers and symptoms they have given you) for situations such as:
- Readings that stay higher or lower than your plan's thresholds despite your usual routine.
- Being unable to keep fluids or food down for an extended period, or diarrhea that will not settle.
- A fever that persists, or an illness that is not improving over the timeframe your clinician described.
- Any uncertainty about your medicines while sick — uncertainty itself is a reason to call.
- Ketones, if checking is part of your plan and they are present or rising as your care team defined.
Call emergency services right away for severe, red-flag symptoms, including:
- Persistent vomiting where you cannot keep any fluids down.
- Confusion, extreme drowsiness, difficulty staying awake, or inability to swallow safely.
- Loss of consciousness or a seizure.
- Signs that could point to diabetic ketoacidosis (DKA) — deep or rapid breathing, fruity-smelling breath, severe abdominal pain, or intense thirst alongside very high readings — which is a medical emergency.
Hypoglycemia matters here too. The ADA describes level 1 low blood sugar as below 70 mg/dL and level 2 as below 54 mg/dL, and a severe low with confusion, inability to swallow, or loss of consciousness is an emergency. The widely taught idea for treating a mild, conscious low is often summarized by the CDC and ADA as the "15-15 rule" — a general approach many educators describe — but how you respond to a low is a decision for your own plan, and your care team's specific instructions replace any general rule. Our guide on low blood sugar symptoms covers recognizing a low, and our overview of symptoms of high blood sugar covers the other direction.
Quick Self-Check: Are You Ready for a Sick Day?
The prompts below are a gentle way to notice whether you have a plan in place before illness arrives. They describe readiness; they do not replace the plan your care team builds with you.
- Do you have a written plan? Could you find your care team's sick-day instructions right now, without hunting?
- Do you know your numbers? Are your personal thresholds for calling — and your care team's phone numbers — somewhere you can reach while feeling unwell?
- Are your supplies ready? Do you have working meter and strips (and ketone supplies if your plan includes them), plus the fluids and foods your clinician suggested?
- Do you know the medicine rule? Have you confirmed what to do about each of your medicines during illness, so you are never guessing?
- Do you know the red flags? Could you name the symptoms that mean call the care team versus emergency services?
If any answer is "not sure," that is a cue to raise it at your next visit rather than during a fever.
Build Your Sick-Day Plan With Your Care Team
Everyone with diabetes benefits from a personal sick-day plan made with a clinician before it is needed, because illness is exactly when clear thinking is hardest and a plan you can follow on autopilot beats decisions made while unwell. Bring these questions to your care team — they are prompts to ask, not instructions to act on:
- How often, and at what times, should I check my blood sugar when I am sick?
- What should I do if my reading is higher than usual, and what number means I call you?
- What should I do if I cannot eat or keep food down, or if my reading runs low?
- Should I continue each of my medicines exactly as prescribed, and would you ever want any changed — and if so, only on your direction?
- Should I check for ketones, and if so, when and what result should prompt a call?
- Which fluids and simple foods do you suggest I keep on hand for sick days?
- Which symptoms mean I should call you, and which mean I should call emergency services?
- What phone numbers should I use during the day and after hours?
Writing the answers down — and keeping them where a family member could find them too — turns general education into a plan you can actually use. Nothing here is dosing, insulin adjustment, or a treatment instruction; those belong to your plan alone, because your clinician weighs your type of diabetes, your medicines, and your overall health when setting your rules. For related planning topics, our guides on does diabetes make you tired and GLP-1 and hypoglycemia touch on symptoms and medicine considerations worth raising at the same visit.
Frequently Asked Questions
Why is my blood sugar high when I am sick even though I am eating less?
When your body fights an illness or infection, it releases stress hormones such as cortisol and adrenaline, which prompt the liver to release more glucose and make cells more resistant to insulin. That combination can raise blood sugar even when you are eating less than usual, so a rise during illness is often the result of the illness itself rather than anything you did. Because illness can move blood sugar either way, checking more often as your care team directs is how you learn what is happening, and your clinician tells you what to do about it.
What are the basic diabetes sick day rules?
As general education attributed to the American Diabetes Association and the Centers for Disease Control and Prevention, the common sick-day pillars are to check your blood sugar more often if your care team directs, keep drinking fluids, keep taking your prescribed medicines unless your clinician tells you otherwise, keep simple carbohydrate and fluid options on hand in case you cannot eat normally, and know the readings and symptoms that mean it is time to call. These are shared starting points rather than a personal prescription, and the version that applies to you is set by your own care team.
Should I stop taking my diabetes medicine when I am sick?
Do not stop, skip, reduce, or change any medicine on your own during illness, even if you feel too unwell to eat or a reading looks unusual. Many sick-day plans have you continue prescribed medicines during illness, and some may be adjusted, but that decision belongs only to your clinician. If you are unsure what to do about a medicine while you are sick, that uncertainty is itself a reason to call your care team rather than to guess.
How often should I check my blood sugar when I am ill?
There is no universal number, because how often to check during illness is set by your care team based on your type of diabetes, your medicines, and your health. Many plans call for checking more frequently than usual during sickness, since illness can push blood sugar higher or, if you cannot keep food down, lower. The value comes from catching changes early and sharing the pattern with your clinician, so follow the specific schedule your care team gives you rather than a generic rule.
When should I call my doctor versus emergency services when sick?
As general education, reach out to your care team, using the numbers and thresholds they gave you, for readings that stay outside your plan's limits, an inability to keep fluids down, a fever that persists, or any uncertainty about your medicines. Call emergency services right away for severe symptoms such as persistent vomiting where you cannot keep fluids down, confusion, extreme drowsiness, inability to swallow, loss of consciousness, or possible signs of diabetic ketoacidosis like deep or rapid breathing, fruity-smelling breath, or severe abdominal pain. Your care team's specific instructions always take priority over any general list.
What is diabetic ketoacidosis and why does it matter on sick days?
Diabetic ketoacidosis, or DKA, is a serious medical emergency in which the body, short on usable glucose in the cells, breaks down fat for fuel and produces acids called ketones that build up in the blood. Illness is a common trigger, which is why some sick-day plans include checking for ketones when readings run high. Warning signs can include deep or rapid breathing, fruity-smelling breath, severe abdominal pain, nausea or vomiting, and intense thirst alongside very high readings. Because DKA is an emergency, any suspicion of it is a reason to seek emergency care right away.
Should I check for ketones every time I get sick?
Whether checking for ketones is part of your sick-day routine depends on your plan, so confirm it with your clinician rather than assuming. Some people are advised to check for ketones when blood sugar runs high during illness, and others are not, and the result that should prompt a call is defined by your care team. If ketone checking is part of your plan, make sure you have the supplies on hand and know when to use them before you get sick, and bring any questions about it to your next visit.
How do I make a diabetes sick day plan before I get sick?
Building a sick-day plan with your clinician before you need it means you can follow it on autopilot when thinking clearly is hardest. Ask your care team how often to check during illness, what to do about high or low readings and the numbers that mean you call, whether to continue each medicine exactly as prescribed, whether to check ketones and when, which fluids and simple foods to keep on hand, and which symptoms mean call the care team versus emergency services. Write the answers down, keep the phone numbers with them, and store the plan where a family member could find it too.
References
- CDC: Diabetes — When You're Sick
- American Diabetes Association: Planning for Sick Days
- NIDDK: Diabetic Ketoacidosis
- CDC: Manage Blood Sugar
- MedlinePlus: Diabetes and Managing Sick Days
Next Steps
Illness raises blood sugar because stress hormones push glucose up while you are fighting an infection — which is why sick days call for a plan rather than improvisation. The pillars here are general education attributed to the ADA and CDC: check more often as directed, stay hydrated, keep taking your medicines exactly as prescribed unless your clinician says otherwise, keep easy options on hand, and know when to call. The version that keeps you safe is the personal one you build with your care team before you ever need it.
If you're ready to build the steady daily habits that support your overall care between sick days alongside any prescribed treatment, the Done With Diabetes™ program offers practical guidance on lifestyle changes for type 2 diabetes covering nutrition, movement, sleep, and daily routines. Get started with Vynleads to take the next step.