Diabetes Sick Day Rules: What a Real Plan Contains, Before You Need It

It's 2am, you have the flu, and you haven't eaten since noon. You check anyway, mostly out of habit, and the meter says 268. That makes no sense to a reasonable person: no food, high number. And then the thought arrives that sends people to the hospital every flu season: *I'm not eating, so I probably shouldn't take my meds.* This guide exists for that exact moment, or better, for the calm week before it. Illness raises blood sugar all by itself, the plan for it is standard and short, and the right time to get yours is while you're healthy.

Why does blood sugar go up when you're sick?

Infection is a stressor, and your body answers stress with hormones: cortisol, adrenaline, glucagon, growth hormone. Those hormones tell the liver to release stored glucose (fuel for the fight) and simultaneously make your cells more resistant to insulin. The result, as MedlinePlus explains, is that blood sugar climbs even on your normal medication doses, and even when you're eating nothing. Sometimes the climb starts a day or two before you feel sick; unexplained highs are occasionally the first symptom of a brewing infection. This is why "no food, high number" makes perfect sense when you're ill, and why the not-eating logic for skipping meds is backwards: sick days are usually when your body needs its medication most.

What does a sick day plan actually contain?

Every sick-day plan, whatever your diabetes type and medications, is built from the same five components. The ADA's sick-day guidance recommends deciding all of this with your care team in advance:

• Check glucose much more often. Normal-day rhythms don't apply. MedlinePlus suggests every 2 to 4 hours while sick, around the clock if things are unstable. A CGM helps, but confirm surprising readings with a fingerstick when you're dehydrated.
• Check ketones. Commonly when glucose runs above 240 mg/dL, and with any vomiting if you have type 1, regardless of the glucose number. Urine strips or a blood ketone meter both work; your plan says which and how often.
• Keep fluids going, strategically. Steady sips all day. If you're eating normally, carb-free fluids (water, broth, sugar-free electrolyte drinks). If you can't eat, alternate carb-free with carb-containing fluids (juice, regular sports drinks, popsicles) so you stay hydrated *and* get enough carbohydrate to take your usual medications safely and avoid a low.
• Keep taking your medications, unless YOUR plan says otherwise. This is the heart of it, and it's covered in its own section below.
• Know your tripwires. The specific numbers and symptoms that mean stop-managing-at-home-and-call. Those are below too.

Should you take your meds when you're sick and not eating?

The general rule in sick-day guidance is continue your medications, because illness pushes glucose up and stopping insulin when you're sick is a fast road to serious trouble. But the honest, complete answer is that some medications have specific sick-day instructions, and this is exactly what your care team's version of the plan is for. Certain classes are commonly paused during dehydration or vomiting, and your clinician will tell you if any of yours are on that list, at what point, and what to do instead. So the question to bring to your next appointment is precise: "Which of my medications have sick-day rules, and what are they?" Write the answer into your plan. What you should never do is decide on your own, at 2am with a fever, which pills and injections to skip. (If metformin side effects are part of what's making sick days miserable, that's its own conversation worth having.)

When to stop managing at home and call

A sick-day plan is a home-management plan with clearly marked exits. Call your care team (they have an after-hours line for exactly this) or seek urgent care when any of these show up:

• Vomiting or diarrhea that goes on more than a few hours, or you can't keep fluids down. Dehydration accelerates everything bad on this list.
• Moderate or large ketones, or ketones that keep rising despite following your plan.
• Glucose that stays very high (many plans use 240 mg/dL as the flag) through multiple checks even though you're doing everything the plan says.
• Any sign of DKA: deep or rapid breathing, fruity-smelling breath, stomach pain, confusion or unusual drowsiness. DKA is a medical emergency; that's a 911-or-ER decision, walked through in the high blood sugar emergency guide.
• A fever that persists, or you simply keep getting worse. "I'm sicker than this plan was written for" is itself a valid reason to call.

Type 1 and type 2: the DKA clock runs differently

With type 1, DKA can develop in a matter of hours once insulin falls short of what the illness demands, which is why type 1 plans check ketones early and often, and why vomiting alone triggers a ketone check. With type 2, the risk is lower but real: serious illness can push anyone into DKA, and some newer glucose-lowering medications are associated with DKA even at near-normal glucose readings, another reason the which-meds-have-sick-day-rules question matters. The plan's skeleton is the same for both; the trigger points and urgency differ, which is why yours should come from your care team with your name on it.

The sick day kit: build it this week

The plan only works if the supplies exist at 2am. One shoebox in the medicine cabinet:

• Ketone strips that aren't expired. The classic failure: the strips in the drawer expired two years ago. Check the date today.
• Fluids, both kinds: carb-free (water, broth, sugar-free electrolyte drinks) and carb-containing (juice boxes, regular sports drink, popsicles).
• Fast glucose sources for lows: tabs or gel, kept with the kit.
• A thermometer, plus whatever over-the-counter remedies your care team has okayed (worth asking, since some cold medicines can nudge glucose or blood pressure).
• The phone numbers: your care team's after-hours line and your pharmacy, written down, not just in a phone that might be dead.
• The written plan itself: one page, from your care team, with your med instructions and your tripwire numbers on it.