If your blood sugar is too high, the first steps are to drink water, check whether you need insulin (if prescribed), and test for ketones if your reading is above 240 mg/dL. Most high blood sugar episodes can be managed at home, but readings that stay elevated or climb with symptoms like confusion, nausea, or fruity-smelling breath need emergency attention.
Know Your Target Numbers
Before you can act on a high reading, it helps to know what “too high” actually means. The American Diabetes Association recommends these targets for most nonpregnant adults with diabetes:
- Before meals: 80 to 130 mg/dL
- One to two hours after starting a meal: below 180 mg/dL
A single reading above these ranges isn’t necessarily dangerous. Blood sugar naturally fluctuates after eating, during illness, and under stress. The concern starts when readings stay elevated, climb above 240 mg/dL, or come with physical symptoms.
Drink Water First
Water is the simplest tool you have. When your blood sugar is elevated, your kidneys work to filter the excess glucose out through urine. The more hydrated you are, the more efficiently that process works. Dehydration slows it down and can make hyperglycemia worse.
Stick to plain water. Soda, juice, and sweetened drinks will push your blood sugar higher. If you’ve been running high for a while, you’ve likely been urinating more than usual already, which means you’re losing fluid faster than normal. Replacing that fluid is one of the most immediate things you can do.
Take Your Prescribed Medication
If you use rapid-acting insulin for corrections, follow the dosing plan your doctor set up for high readings. This is sometimes called a “correction dose” or “sliding scale.” Don’t take extra beyond what your plan allows, since stacking insulin doses can cause a dangerous low later.
If you take oral medications and your blood sugar is persistently high despite taking them as directed, that’s a signal your treatment plan may need adjusting. Don’t double up on pills without guidance.
Test for Ketones Above 240 mg/dL
This is the step many people skip, and it matters. When your blood sugar reaches 240 mg/dL or higher, your body may start burning fat for fuel because it can’t use the glucose in your blood. That fat breakdown produces ketones, acidic byproducts that can build up to dangerous levels.
You can check for ketones with an over-the-counter urine test kit available at most pharmacies. The American Diabetes Association recommends testing when your blood glucose is above 200 mg/dL. If the test comes back positive, call your doctor. A positive ketone result with high blood sugar can signal the early stages of diabetic ketoacidosis (DKA), a medical emergency.
Be Careful With Exercise
Light physical activity, like a 15-minute walk, can help lower moderately high blood sugar by moving glucose into your muscles where it gets used as energy. But there’s a threshold where exercise becomes risky instead of helpful.
If your blood sugar is above 270 mg/dL, test for ketones before doing any physical activity. Exercising with ketones present forces your body to produce even more of them, which can trigger ketoacidosis. If your ketone test is positive, skip the workout entirely. Focus on hydration and insulin (if prescribed) to bring your numbers down first, and wait until a follow-up ketone test shows they’ve cleared.
Below 270 mg/dL with no ketones, gentle movement is generally safe and effective. A short walk after a high post-meal reading is one of the fastest non-medication tools available.
Look at What Caused the Spike
Once you’ve addressed the immediate high, it’s worth tracing back to the cause so you can prevent the next one. The most common culprits:
- Carbohydrate miscounting: A meal with more carbs than you estimated, especially refined carbs like white bread, rice, or pasta, will spike blood sugar faster and higher.
- Missed or mistimed medication: Taking insulin too late relative to a meal, or forgetting a dose of oral medication, leaves glucose unmanaged.
- Illness or infection: Your body releases stress hormones when fighting off sickness, which raises blood sugar even if you haven’t eaten differently.
- Stress and poor sleep: Both trigger hormonal responses that increase glucose production in the liver.
- Dehydration: Less water in the bloodstream means the same amount of glucose is more concentrated, producing a higher reading.
Keeping a brief log of your readings alongside meals, medication timing, and how you felt can reveal patterns that a single reading won’t show.
Symptoms That Need Emergency Care
Most high blood sugar episodes resolve with hydration, medication, and time. But two conditions can develop when hyperglycemia goes untreated or escalates, and both are medical emergencies.
Diabetic ketoacidosis (DKA) is more common in type 1 diabetes but can happen in type 2. Warning signs include nausea, vomiting, stomach pain, fruity-smelling breath, and rapid breathing. These symptoms mean ketone levels have climbed high enough to make your blood acidic.
Hyperosmolar hyperglycemic syndrome (HHS) tends to develop in type 2 diabetes, often over days. Symptoms include extreme thirst, very frequent urination that then decreases, dry mouth, fever, weakness, confusion, seizures, and in severe cases, coma. HHS can also cause difficulty with movement and speech.
If you or someone around you shows confusion, difficulty breathing, persistent vomiting, or blood sugar that won’t come down despite correction doses, get to an emergency room. These conditions progress quickly and require IV fluids and close monitoring that can’t be managed at home.
When Highs Keep Happening
A single high reading after a large meal is normal. Several readings above your target range over the course of a week, or fasting numbers that consistently land above 130 mg/dL, suggest your current management plan isn’t keeping up. This could mean your medication type or dose needs adjustment, your meal plan needs reworking, or there’s an underlying factor like a new medication, hormonal change, or developing insulin resistance that’s shifting the equation.
Tracking your numbers for a few days before that appointment gives your provider something concrete to work with. Patterns in the data, like highs every morning or spikes after dinner, point to specific adjustments rather than guesswork.