If your blood sugar is high, the first steps are to drink water, check whether you need a correction dose of insulin (if you take it), and avoid sugary foods. What counts as “high” depends on timing: a normal target before meals is 80 to 130 mg/dL, and a reading two hours after eating should be below 180 mg/dL. Anything consistently above those ranges needs attention, and the higher it goes, the more urgently you need to act.
Drink Water First
Dehydration both causes and worsens high blood sugar. When glucose builds up in your bloodstream, your kidneys try to flush it out through urine, which pulls water with it. That fluid loss concentrates the remaining sugar even further. Drinking water helps your kidneys clear excess glucose and rehydrates you at the same time. Plain water is ideal. Avoid juice, regular soda, or sports drinks, all of which will push your blood sugar higher.
Take Your Medication if You’ve Missed It
One of the most common reasons for an unexpected spike is simply skipping or mistiming a dose of diabetes medication. If you use insulin, you may have a correction dose built into your plan. A correction dose is based on your individual “insulin sensitivity factor,” which tells you how much one unit of rapid-acting insulin will lower your blood sugar. For many people, one unit drops blood sugar by roughly 50 mg/dL, but this varies widely, from 15 to over 100 mg/dL per unit. Your doctor or diabetes educator sets this number for you.
If you don’t take insulin, check whether you’ve missed your oral medication. Taking it as directed is often enough to bring a moderate spike back down within a few hours. Don’t double up on a dose to compensate unless your care team has specifically told you to.
Move Your Body, but Check for Ketones First
Light physical activity, like a 15- to 30-minute walk, helps your muscles pull glucose out of your bloodstream for energy. For moderate highs, this can make a noticeable difference. But there’s an important safety check: if your blood sugar is above 240 to 270 mg/dL, test your urine or blood for ketones before exercising. Ketones are acids your body produces when it starts burning fat instead of glucose, a sign that insulin levels are dangerously low.
If ketones are present, do not exercise. Physical activity when ketones are elevated can trigger a serious condition called diabetic ketoacidosis. Instead, focus on hydration and insulin correction, and wait until a follow-up test shows no ketones before you get moving again. If you test negative for ketones and feel well, exercise is safe and helpful even at higher readings.
Eat Strategically at Your Next Meal
What and how you eat over the next several hours matters. The order in which you eat your food has a measurable effect on how high your blood sugar climbs afterward. Eating vegetables and protein before any carbohydrates slows the rate at which sugar enters your bloodstream. Fats and protein slow digestion overall, and fiber from vegetables creates a gel-like matrix in your small intestine that reduces absorption speed. When simple carbs arrive last into that environment, the post-meal glucose spike is significantly blunted.
A practical approach: start your next meal with a salad or cooked vegetables, eat your protein next, and save any bread, rice, or starchy sides for last. Eat slowly. And for the time being, limit highly processed foods, snack foods, and anything with added sugars.
Figure Out What Caused the Spike
If you didn’t simply eat too many carbs or miss a dose, several other factors could be responsible. Illness, infection, injury, or surgery all raise blood sugar, sometimes dramatically, because your body releases stress hormones that trigger glucose production in the liver. Emotional stress does the same thing. Hormonal shifts during menstrual cycles or menopause can cause unpredictable fluctuations. Certain medications, particularly steroids like prednisone, are well known for pushing blood sugar up. Even dehydration on its own can be enough to elevate your readings.
Identifying the cause helps you respond appropriately. A spike from a one-time stressful event will resolve differently than one caused by a new medication you’ll be taking for weeks.
Know When It’s an Emergency
Most blood sugar spikes are uncomfortable but manageable at home. There are specific thresholds, though, where the situation becomes dangerous.
- Above 240 mg/dL: Test for ketones. Check your blood sugar every four to six hours until it comes down.
- Above 250 mg/dL with symptoms: Early warning signs include extreme thirst and urinating far more than usual. If these persist alongside a high reading, contact your care team.
- 300 mg/dL or above that won’t come down: Go to the emergency room or call 911. At this level, you’re at risk for diabetic ketoacidosis, which can progress quickly.
Symptoms of ketoacidosis include fast, deep breathing, fruity-smelling breath, nausea and vomiting, stomach pain, severe fatigue, and dry skin and mouth. If you feel drowsy or disoriented at any point while your blood sugar is elevated, that’s a 911 situation regardless of the number on your meter.
What to Watch Over the Next Few Hours
After you’ve taken corrective steps, recheck your blood sugar in one to two hours. A single high reading that responds to water, activity, and proper medication is usually nothing to worry about beyond adjusting your approach for next time. Two or more high readings several hours apart, especially if they’re above your target range, signal that something in your management plan needs to change.
If your blood sugar stays elevated over multiple checks, or if high readings are becoming a pattern over several days, that’s a sign to talk with your care team about adjusting your medication doses, meal plan, or both. High blood sugar that lingers isn’t just uncomfortable in the moment. Over time, it damages blood vessels, nerves, and organs, so catching and correcting a pattern early makes a real difference.