If you’re sick with gestational diabetes and your numbers suddenly don’t make sense — you’re not the only one. One day you’re doing your usual routine, and the next day you feel unwell, can’t eat normally, and your blood sugar is higher anyway.
Julija note: This is one of those moments where gestational diabetes feels wildly unfair. You’re not “failing.” Your body is dealing with illness + pregnancy hormones at the same time.
Yes — illness can raise blood glucose levels even if you’re eating less. Infections and stress hormones can increase insulin resistance, and dehydration can push numbers up and make them harder to manage.
The other big piece: if you can’t keep food down (especially with vomiting), your body may start producing ketones. That’s why a pregnancy sick-day plan (based on your care team’s guidance) is usually about two things:
Keeping fluids going (drink, sip, repeat)
Preventing ketones while still managing blood glucose
Gestational diabetes happens when pregnancy hormone changes make the body less effective at using insulin. When you’re sick, your body adds another layer of stress response on top of that.
Here’s what can happen:
Illness triggers stress hormones (like cortisol), which can make your blood sugar levels rise.
Your body may release more glucose into the blood to fuel your immune system.
Infections can push numbers up (even before you feel really sick).
Dehydration can concentrate glucose and make readings higher.
So yes: you can eat less, and still see your blood glucose go up. Annoying, but normal.
When you’re sick with gestational diabetes, the goal is not perfect tracking — it’s safety.
Drink plenty (in small, steady sips)
Try to eat something if you can (even small amounts)
Test glucose more often than usual
Check ketones if you’re not eating, vomiting, or your provider told you to
Know when to call your doctor / midwife / healthcare team
If you’re vomiting or can’t stomach much, think “sips, not glasses.”
Try:
Water (tiny sips every few minutes)
Broth
Electrolyte drinks that don’t spike you (or diluted versions)
Herbal tea if tolerated (check with your provider first)
Milk if it sits well for you (some women tolerate it better than plain water)
Signs you may be getting dehydrated:
Dark urine
Dizziness, dry mouth
Feeling weak or “shaky”
Julija note: If you can’t keep fluids down for several hours, don’t wait it out. This is one of those times where going in can actually prevent bigger problems.
On a normal gestational diabetes day, we aim for healthy eating: carbs + protein + fat + fiber.
On a sick day, the goal is: “What can I keep down?”
Stick to your usual diet structure and make gentle, simple food choices:
Soup + protein (chicken, tofu, eggs)
Yogurt + nuts
Eggs + toast
A balanced dinner you’d normally tolerate
Start with bland, easy foods and build up:
Crackers or toast
A small bowl of rice
Unsweetened applesauce
Yogurt
Small portions of carbs you tolerate
If you can, add a little protein or fat (even a bite or two): cheese, nut butter, eggs.
Why carbs matter here: if you go too low on carbs (especially if you’re barely able to eat), your body can start producing ketones. And sometimes going too low can even backfire — your liver can dump glucose to compensate for the lack of fuel, so blood sugar can rise even if you didn’t eat any carbs.
When you’re sick, it’s common for your blood sugar pattern to change — sometimes quickly. Many care teams recommend a bit more frequent testing during illness, especially if your numbers are running higher than usual or you’re on insulin/meds.
Keep checking your usual fasting + post-meal blood sugars (per your clinic’s timing).
If numbers are climbing, you’re not eating much, or you feel “off,” consider adding one extra check (for example, before bed) and note what’s going on (fever, vomiting, meds, dehydration).
More data helps your healthcare team interpret what’s happening and adjust your plan if needed.
Ketones are chemicals your body produces when it’s breaking down fat for energy — often because you’re not eating enough, you’re vomiting, you’re dehydrated, or you’ve gone a long time without carbs.
In pregnancy, we generally try to avoid ketones — not because you did something “wrong,” but because they can be a sign your body is under-fueled or under stress (which is common with illness and HG).
Quick reassurance: a small/trace amount of ketones can happen, especially first thing in the morning, after vomiting, or when you haven’t been able to eat much. It’s often your body saying: “I need fluids and fuel.”
What matters is the trend (are they rising?) and the context (are you sick, dehydrated, losing weight, or unable to keep food down?).
If you want a deeper breakdown, here’s the full guide on What ketones mean in GD, when to worry, and what to do next?
You’ve been vomiting or can’t keep food down
You’re barely eating (especially carbs)
You’re dehydrated
Your blood sugar is persistently high
Your provider gave you a ketone plan
Most people check ketones using urine strips (yes — it’s a urine test).
If ketones are moderate/large, if you can’t keep fluids down, or if you’re worried, call your doctor/midwife — especially during pregnancy.
If you’re using insulin injections (or any GD medication), illness can change what your body needs.
Don’t stop insulin on your own unless your healthcare team tells you to.
Some people need enough insulin to cover stress hormones during illness.
Vomiting can make timing tricky — this is exactly when you want guidance.
If you’re unsure, call your healthcare team and ask for a sick-day insulin plan.
Gestational diabetes can come with an increased risk of certain health issues, including being more prone to infections like UTIs. And infections can elevate blood sugar.
If you have symptoms like burning when peeing, pelvic pain, fever, or you just feel “off” in a way that’s getting worse, call your doctor/midwife. Early treatment can reduce health risks.
If you want a deeper read on infections in pregnancy + GD, here’s a helpful post on Yeast infection with gestational diabetes.
Gentle movement (like a short walk) can help lower blood sugar levels — but only if you’re not dizzy, dehydrated, or feverish.
If you’re sick-sick, rest is also treatment.
Call your healthcare team if:
You can’t keep fluids down for several hours
Vomiting is persistent
You have signs of dehydration (very dark urine, dizziness)
Your blood glucose levels stay high despite your usual plan
You have moderate/large ketones
You’re worried about baby movement
Go to urgent care/hospital if symptoms feel severe, you’re getting worse quickly, or you can’t stay hydrated.
Also: severe headache, vision changes, or swelling can be warning signs for conditions like preeclampsia (which is associated with gestational diabetes). If you have those symptoms, don’t wait.
If you get sick during pregnancy, please don’t panic — most GD mamas still go on to have healthy pregnancies and healthy babies.
Your team may keep a closer eye on baby as you get closer to birth. And after delivery, babies born to moms with GD usually get a few blood sugar checks, because some can have low blood sugar (hypoglycemia) right after birth. It’s common, and it’s exactly why the checks exist: to spot it early and keep you and baby safe.
Gestational diabetes increases the risk of developing type 2 diabetes later in life, and it can also mean a higher chance of GD in subsequent pregnancies.
That’s not meant to scare you — it’s just a reminder that postpartum follow-up and support matters. Read more on OGTT After Gestational Diabetes (6–12 Weeks Postpartum): What It Means + How to Prepare.
If you’re ill with gestational diabetes and your numbers are higher, it doesn’t mean your diet suddenly “stopped working.” It means your body is fighting something — and that can affect glucose.
Focus on fluids, keep food as simple as you need, watch for ketones, and lean on your healthcare team for support. You’re doing the right things for you and your baby.
In most cases, once the illness passes, blood sugars settle back toward your usual pattern. But remember: pregnancy is still progressing in the background, and insulin resistance can change week to week. So if you’re feeling better and your numbers still aren’t returning to “normal for you” after a few days, that’s a good sign to check in with your care team — you may just need a small plan adjustment (and sometimes medication support), not a stricter diet.
1. Can being sick raise blood sugar even if I’m not eating much?
Yes. Illness can raise stress hormones and increase insulin resistance, which can elevate blood glucose even if you’re eating less.
2. What if I’m vomiting and can’t keep carbs down?
Focus on fluids first, then try small amounts of bland carbs as tolerated (toast, crackers, rice). If you can’t keep anything down or you’re worried about ketones, call your healthcare team.
3. When should I check ketones?
If you’re vomiting, not eating, dehydrated, or your provider told you to monitor ketones, check using urine strips and follow your care team’s plan.
4. Should I keep taking insulin if I’m sick?
Don’t stop insulin without guidance. Illness can change insulin needs, so contact your healthcare team for a sick-day plan.
Get a Free 20-Day Shopping List
