Diabetes Sick-Day Plan: When to Check Ketones and Get Help

Illness can turn an ordinary diabetes routine into a moving target. A fever, stomach bug, infection, pain, or poor sleep may make glucose harder to manage even when you are eating less than usual. That is why a sick-day plan works best when it is written before you need it: it gives you a short list of what to check, whom to call, and when not to wait.

This guide is a planning tool, not a substitute for the instructions from your own diabetes team. Your medication, insulin, pregnancy status, kidney function, and history of low or high glucose can all change the safest next step. If you take insulin, use an insulin pump, have had diabetic ketoacidosis (DKA), or have been given ketone instructions, keep those individual directions at the center of your plan. [1]

A sick-day plan is a prepared response, not a test of willpower

When you are unwell, stress hormones can raise glucose and illness can make food and fluids harder to keep down. At the same time, taking less food than usual can raise the risk of low glucose for people using insulin or certain other medicines. Neither a high number nor a low appetite means you have failed at diabetes care. It means the usual routine may need the backup plan you and your clinician prepared. [2]

A useful plan fits on one page and answers four questions:

• How often should I check glucose, and what should I write down?
• When should I check ketones, and which test do I have at home?
• Which medicines or insulin instructions apply to me when I cannot eat normally?
• Which symptoms, readings, or ketone results mean I should call now or seek emergency care?

Do not wait until you are vomiting, exhausted, or unsure about a dose to ask those questions. Put your diabetes team’s phone number and after-hours instructions where another person can find them too.

Who should make a plan?

Anyone with diabetes can benefit from knowing what to do when sick, but a written plan is especially important for people who use insulin, have type 1 diabetes, use a pump, have had DKA, are pregnant, or have been told to monitor ketones. People with type 2 diabetes can develop serious high-glucose illness too, so “I do not use insulin”is not a reason to guess when symptoms are significant.

Children, older adults, and people who need help managing medicines need a plan that includes a caregiver. If you are pregnant, follow the pregnancy-specific thresholds and contact instructions from your prenatal team rather than a general article. The same is true if you have kidney disease, a history of severe lows, or a medication plan with special sick-day rules.

Set up the plan before you are sick

Start with a brief conversation at a routine diabetes visit, then keep the finished plan with your supplies. Include the name and number of your primary diabetes contact, a pharmacy, an after-hours number, and an emergency contact. Write your usual medication and insulin schedule exactly as prescribed, plus the clinician’s instructions for illness. Never invent a dose change or stop a prescribed medicine based on a generic checklist.

Keep the supplies your own plan calls for together: your meter and in-date strips, a backup way to charge or power a device if you use one, ketone strips or a blood-ketone meter if recommended, a thermometer, a written medication list, water or other fluids you can tolerate, and easy-to-digest carbohydrate-containing foods if your team advises them. The American Diabetes Association also recommends preparing a sick-day kit in advance. [1]

A simple record can prevent confusion when you feel unwell. Note the time, glucose result, ketone result if checked, temperature, vomiting or diarrhea, fluids kept down, medicines taken, and any call you made for advice. Our guide to keeping a blood sugar log can help you keep those notes focused rather than overwhelming.

When illness starts: use the first few hours well

First, pause and assess the situation. Are you breathing normally? Can you keep fluids down? Are you alert enough to follow your plan? Are you having symptoms that are unusual for you? If the answer raises concern, call for help early rather than trying to manage alone.

Next, follow the monitoring schedule your clinician gave you. CDC guidance says illness can make blood sugar harder to manage and notes that a clinician may ask for more frequent checks; its public sick-day guidance suggests checking glucose every four hours and recording the results. [2] Your own interval may be different. A continuous glucose monitor can show a trend, but use the confirmation and symptom instructions that came with your device and care plan. For a refresher on the strengths and limits of each tool, see Blood Glucose Meter vs. CGM.

Continue prescribed diabetes medicines and insulin unless your clinician has specifically told you otherwise. Being unable to eat does not automatically mean insulin can be skipped. If you are unsure about a medicine, dose, pump issue, or dehydration risk, that uncertainty itself is a reason to contact your diabetes team or pharmacist promptly.

When to check ketones

Ketones are acids made when the body does not have enough usable insulin and begins breaking down fat for fuel. A rising ketone level can be an early sign of DKA, a serious emergency. DKA is most common in type 1 diabetes, but it can occur in people with type 2 diabetes as well. [3]

Use the threshold your clinician gave you first. Public guidance is not identical: CDC advises checking urine ketones when you are sick or when glucose is 250 mg/dL or above, while an ADA public sick-day guide instructs people to test every four to six hours if glucose is above 200 mg/dL. That difference is a reason to clarify your personal action threshold before illness—not to average the two numbers or wait for the higher one. [3] [1]

Question	Why it matters	Best next step
Am I sick or is glucose higher than the action threshold in my plan?	Illness and inadequate insulin can increase the chance of ketones.	Follow your prescribed ketone-testing instructions.
Do I have nausea, vomiting, abdominal pain, fast or deep breathing, or fruity-smelling breath?	These can be warning signs of DKA, especially with high glucose or ketones.	Seek urgent medical guidance; use emergency care for severe symptoms.
Is the result positive, moderate, large, or higher than my plan allows?	The number needs context from your type of test and care plan.	Call the diabetes team or use the urgent instructions you were given; do not try to self-treat a concerning result from an article.

Urine and blood ketone tests are not interchangeable in timing or units. Use the method and interpretation your clinician taught you, check expiration dates, and keep the package instructions. A ketone result is a safety signal, not a diagnosis you should interpret in isolation.

Know the signs that should not wait

Call 911 or go to an emergency department right away for trouble breathing, vomiting with inability to keep food or drinks down, fruity-smelling breath, confusion, severe drowsiness, or multiple symptoms of DKA. CDC also advises urgent evaluation when blood glucose stays at 300 mg/dL or above, or when ketones are high. [3] If you are too sick to think clearly, ask someone else to call or drive; do not drive yourself.

Less dramatic problems can still deserve a same-day call. Contact your care team according to your plan when you have positive ketones, glucose outside your action range that is not improving, recurring lows, uncertainty about a dose, a possible pump or supply problem, fever or illness that is worsening, or you simply cannot keep up with fluids. The goal is timely advice, not trying to prove that you can handle it alone.

If glucose is low and you are awake and able to swallow, use your individualized low-glucose plan first. Our separate guide to treating a low blood sugar episode safely explains the general 15-15 approach and its limits. Severe low glucose, inability to swallow, or a person who needs help are emergencies.

Avoid the common sick-day mix-ups

Do not use a home reading to diagnose yourself

A meter, CGM, or ketone strip can be valuable for action during illness, but it does not replace a clinical assessment. If a meter result seems surprising, clean and dry your hands, use an in-date strip, and follow the device instructions; then place the repeat in the context of symptoms and your plan. Our guide to checking an unexpected meter result covers a careful recheck.

Do not confuse “not eating”with “no insulin needed”/h3>

Illness can raise glucose even when appetite is low. Insulin needs and medication instructions are individual, which is why a prewritten plan and a prompt call are safer than a one-size-fits-all adjustment.

Do not wait for a perfect pattern

One concerning combination—such as high ketones with vomiting or unusual breathing—matters more than a beautifully complete log. Record what you can, but seek help when the plan tells you to do so.

Frequently asked questions

Should every person with diabetes keep ketone strips at home?

Ask your diabetes team. Ketone testing is especially important for many people who use insulin or are at risk of DKA, but the best supplies and action thresholds depend on your situation.

Can I wait until my glucose is very high before checking ketones?

No universal number is right for everyone. CDC and ADA public materials use different action thresholds, and your clinician may use another one. Confirm your personal sick-day instructions before you need them.

What if I cannot eat?

Follow the fluid, carbohydrate, medication, and call instructions in your individual plan. If you cannot keep liquids down, have vomiting, or are unsure about medicines or insulin, seek medical guidance promptly. [2]

Can a CGM replace ketone testing?

No. A CGM measures interstitial glucose, not ketones. Follow the ketone-testing instructions in your sick-day plan even if you use a CGM.

Bottom line

A good diabetes sick-day plan is short, personal, and ready before illness disrupts your routine. Keep your supplies and contacts together, follow the monitoring and medication directions written for you, check ketones when your plan calls for it, and treat breathing problems, vomiting, high ketones, confusion, or persistent very high glucose as reasons to get help quickly.

References

1. American Diabetes Association. Diabetes and Planning for Sick Days. Accessed October 20, 2026.
2. Centers for Disease Control and Prevention. Managing Sick Days. Updated May 15, 2024. Accessed October 20, 2026.
3. Centers for Disease Control and Prevention. Diabetic Ketoacidosis. Updated May 15, 2024. Accessed October 20, 2026.