Diabetes Sick Day Rules: What to Do When You're Sick (T1 and T2)

You wake up with a fever, a sore throat, and zero appetite. You haven't eaten all day — so why is your blood sugar 240?

It's one of the most confusing parts of living with diabetes. Illness pushes blood sugar in the wrong direction even when food isn't involved, and the day you feel least capable of managing anything is the day your numbers need the most attention.

That's exactly why sick day rules exist: a short, pre-decided plan so you're not making judgment calls at 3am with a fever. Here's what those rules are, for both type 1 and type 2.

Quick answer

• Keep taking your diabetes medication or insulin — even if you're not eating. Illness usually raises blood sugar, so stopping is the opposite of what your body needs. Ask your care team ahead of time whether your doses change when you're sick.
• Test more often — every 4 hours is the standard, day and night
• Check ketones every 4–6 hours if you have type 1, or if you have type 2 and your blood sugar is running above 240 mg/dL
• Drink 4–6 oz of fluid every half hour — sugar-free if your numbers are high, sugared if they're dropping
• Aim for about 50g of carbs every 4 hours if you can't eat normal meals
• Call your care team for vomiting or diarrhea past 6 hours, a fever over 101°F for 24 hours, blood sugar over 250 that won't come down, or moderate-to-high ketones

Why illness raises blood sugar — even when you're not eating

When you're sick, your body releases stress hormones — cortisol, adrenaline, glucagon — to help fight off the infection. Those hormones tell your liver to dump stored glucose into your bloodstream, and they make your cells more resistant to insulin at the same time.

The result: more sugar coming in, less of it getting used. That's why a stomach bug can send your numbers up even on a day when you've eaten nothing but a few crackers.

Two things follow from that:

1. Not eating is not a reason to skip insulin. Your body is producing glucose internally, and it still needs insulin to handle it. For people with type 1 especially, skipping insulin during illness is the fastest route to diabetic ketoacidosis (DKA).
2. You can't predict which way you'll go. Most illnesses drive blood sugar up. But vomiting, diarrhea, and not eating can drive it down hard — which is why the plan includes both sugar-free and sugared fluids.

A small number of illnesses do the reverse and cause lows. That's the whole reason the rules are built around testing more, not around guessing.

The 6 sick day rules

Print these, screenshot them, tape them inside a cabinet. Whatever gets them in front of you when you feel awful.

1. Never stop your insulin or diabetes medication. Some doses may need adjusting, but "I'm not eating so I skipped it" is the single most common sick-day mistake. If you take insulin, ask your care team now — while you feel fine — what your sick-day dosing plan looks like.

2. Test your blood sugar every 4 hours. Including overnight. Set an alarm.

3. Check ketones every 4–6 hours. Always if you have type 1. If you have type 2, check any time your blood sugar is over 240 mg/dL, and always if you're on an SGLT2 inhibitor (Jardiance, Farxiga, Invokana), which can cause ketones even at normal glucose levels.

4. Keep fluids going — 4 to 6 ounces every half hour. Water or broth if your sugar is high; regular soda, juice, or an electrolyte drink if it's low or you can't keep carbs down. Small sips beat big gulps when you're nauseated.

5. Get about 50 grams of carbs every 4 hours. Not a real meal — applesauce, crackers, toast, popsicles, regular Jell-O, juice. Whatever stays down.

6. Write everything down. Time, blood sugar, ketones, temperature, what you ate, what you took. If you end up calling your doctor or heading to urgent care, this log is the single most useful thing you can hand them.

What "test every 4 hours" actually looks like

Six checks in 24 hours instead of your usual two or four. That adds up fast, and it's why sick-day prep is really supply prep — the worst time to discover you're down to three lancets is at 2am on day two of the flu.

A realistic sick day looks something like:

If your hands are cold or you're dehydrated, getting a good drop gets harder — warm your hands under water first and let your arm hang for a few seconds. Our step-by-step guide to checking your blood sugar correctly covers the technique details that matter most when you're testing this often, and when to test your blood sugar explains how sick-day timing differs from your normal routine.

One note if you wear a CGM: dehydration and rapid glucose swings both widen the gap between sensor readings and actual blood glucose. Sick days are exactly when a fingerstick confirmation earns its keep.

Ketones: when to check and what the numbers mean

Ketones are what your body produces when it burns fat for fuel because it can't get glucose into cells. A few are normal. A lot, combined with high blood sugar, is the early stage of DKA — a genuine emergency.

You can check with urine strips (cheap, available at any pharmacy) or a blood ketone meter (faster and more accurate, especially for type 1).

Buy the strips before you need them and check the expiration date — urine ketone strips often expire 6 months after opening, and a fever is a bad time to find out yours are from two winters ago.

What to eat and drink when nothing sounds good

The goal isn't nutrition. It's keeping fluids and a steady trickle of carbs going.

If your blood sugar is high (or normal): water, broth, sugar-free popsicles, unsweetened tea, diet ginger ale, sugar-free electrolyte drinks.

If your blood sugar is low or dropping: regular soda (flat is easier on the stomach), apple or grape juice, regular Jell-O, regular popsicles, sports drinks, honey in tea.

Carb sources that usually stay down: saltines, plain toast, unsweetened applesauce, plain rice, bananas, broth-based soup, oatmeal.

A quick swap chart — roughly 15g of carbs each:

• 1/2 cup regular juice or soda
• 1 slice toast
• 6 saltine crackers
• 1/2 cup unsweetened applesauce
• 1 regular popsicle
• 1/2 cup regular Jell-O

Four of those over four hours gets you to the ~50g target. If you can't keep anything down for more than 4 hours, that's a call-your-doctor moment, not a wait-it-out moment.

Build your sick day kit before you need it

Everything on this list should live in one box or bag, already assembled, so a sick you doesn't have to shop:

• Extra lancets — enough for 6+ checks a day for several days
• Extra test strips (check expiration dates twice a year)
• Ketone strips or a blood ketone meter
• A thermometer
• Sugar-free electrolyte drinks and regular soda or juice
• Shelf-stable carbs: applesauce cups, crackers, juice boxes
• Glucose tablets or gel for lows
• A written copy of your sick-day plan and your care team's after-hours number
• A sharps container for the extra lancets you'll go through

If you don't have a base kit yet, the Pip Diabetes Starter Kit covers most of the testing side in one box, and it's a straightforward way to build a second set of supplies that stays sealed until you actually need it. For the day-to-day testing itself, Pip's single-use lancets are worth having stocked deep for sick days specifically — each one is individually capped, so you twist off the cap, press it to your fingertip, and it fires and retracts on its own. Nothing to load, nothing to reset, nothing to fumble with at 4am with a fever. When you're going through six a day, the Pip Travel Safe pocket sharps container keeps the used ones contained on the nightstand instead of loose on a bedside table.

Newly diagnosed and building your supply baseline from scratch? Start with the newly diagnosed first-week survival guide and add the sick-day items on top.

When to call your care team — and when to go to the ER

Call your doctor if:

• Vomiting or diarrhea lasts more than 6 hours
• You can't keep fluids down for more than 4 hours
• Fever over 101°F for 24 hours
• Blood sugar stays over 250 mg/dL despite taking your usual medication
• Blood sugar drops below 60 mg/dL and won't come up
• Ketones are moderate or higher
• You've been unable to eat for more than 24 hours
• You've lost 5+ pounds since getting sick

Go to the emergency room if:

• Large ketones with high blood sugar
• Trouble breathing, or breathing that's deep and rapid
• Fruity-smelling breath
• Confusion, extreme drowsiness, or trouble staying awake
• Persistent vomiting with high blood sugar and ketones
• Chest pain

The ADA's sick day planning guidance and the CDC's guidance on diabetes and flu both make the same core point: the plan works because you wrote it down before you got sick. Ask your care team for your personal version at your next appointment — including whether any of your medications should be paused during illness, since some (like metformin and SGLT2 inhibitors) sometimes are.

The bottom line

Illness raises blood sugar even when you're not eating, so the rules are: keep taking your medication, test every 4 hours, check ketones every 4–6, keep fluids and small carbs going, write it all down, and know your call-the-doctor thresholds ahead of time.

The prep takes 20 minutes on a day you feel fine. It pays for itself the first time you're too sick to think clearly. And like managing blood sugar in extreme heat, most of the work is front-loaded — the plan does the heavy lifting later.

Always check with your care team before changing how you take any medication.

FAQ

Should I stop taking insulin if I'm not eating while sick?
No. Illness raises blood sugar through stress hormones whether or not you eat, so your body still needs insulin. Your dose may need adjusting — ask your care team for a sick-day dosing plan in advance — but stopping insulin entirely, especially with type 1, significantly raises the risk of diabetic ketoacidosis.

How often should I check my blood sugar when I'm sick?
Every 4 hours, including overnight. That's roughly six checks in 24 hours instead of your usual routine, so make sure you have the lancets and strips to cover several days.

When do I need to check ketones?
Every 4–6 hours while you're sick if you have type 1. If you have type 2, check whenever your blood sugar is above 240 mg/dL, and always if you take an SGLT2 inhibitor like Jardiance, Farxiga, or Invokana — those can cause ketones even when glucose looks normal.

What can I eat when I'm sick and have no appetite?
Aim for about 50 grams of carbs every 4 hours from whatever stays down: crackers, toast, unsweetened applesauce, popsicles, regular Jell-O, juice, or broth-based soup. If your blood sugar is high, use sugar-free fluids; if it's low or dropping, use sugared ones.

Can I take over-the-counter cold medicine with diabetes?
Many are fine, but some syrups and cough drops contain a lot of sugar, and some decongestants can raise blood sugar and blood pressure. Look for sugar-free versions where possible and ask your pharmacist — they can check interactions with your specific medications in about a minute.