If your blood sugar is high, the most effective immediate steps are drinking water, moving your body, and, if you use insulin, taking a correction dose as prescribed. A reading above 180 mg/dL is generally considered above target, and anything above 240 mg/dL warrants checking for ketones. What you do next depends on how high the number is and whether you’re experiencing symptoms.
Drink Water First
Water is one of the simplest tools for bringing down a high reading. When blood sugar is elevated, your kidneys try to filter out the excess glucose by pulling water into your urine. This is why high blood sugar makes you pee more often and feel thirsty. Drinking water supports that process, helping your body flush glucose out faster while replacing the fluid you’re losing.
Dehydration actually makes the problem worse. Less water in your body means glucose becomes more concentrated in your blood, pushing the number even higher. There’s no single magic volume to aim for, but steady sipping over the next hour or two is a good starting point. Avoid juice, soda, or sweetened drinks, which will only add more sugar.
Move Your Body
Physical activity lowers blood sugar through a mechanism that works even when insulin isn’t doing its job well. When your muscles contract during movement, your cells pull glucose in and burn it for energy whether insulin is available or not. That makes exercise one of the fastest non-medication options you have.
You don’t need an intense workout. A 15 to 30 minute walk, light cycling, or even doing household chores can make a noticeable difference. The key is getting your muscles working. One important exception: if your blood sugar is above 240 mg/dL and you have ketones present (more on that below), exercise can actually raise blood sugar further. Check for ketones first if you’re in that range.
Use Your Correction Dose if You Take Insulin
If you’re on rapid-acting insulin, your doctor has likely given you a correction factor, sometimes called an insulin sensitivity factor. This tells you how much one unit of insulin will lower your blood sugar. The formula is straightforward: subtract your target blood sugar from your current reading, then divide by your correction factor. For example, if your blood sugar is 250 mg/dL, your target is 150, and your correction factor is 50, that’s a 2-unit correction dose.
This math is personal to you. Your correction factor, your target, and your dosing schedule are all set by your care team based on how your body responds to insulin. Don’t guess at a correction dose if you haven’t been given one. Taking too much insulin carries its own serious risks.
After taking a correction dose, wait at least two hours before rechecking and dosing again. Stacking insulin doses too close together is a common cause of dangerous lows.
Check for Ketones Above 240 mg/dL
When your blood sugar climbs above 240 mg/dL, your body may start breaking down fat for energy instead of glucose. That process produces ketones, which are acidic compounds that can build up in your blood and become dangerous. This is the pathway to diabetic ketoacidosis (DKA), a medical emergency most common in people with type 1 diabetes but possible in type 2 as well.
You can check ketones with urine test strips available at most pharmacies, or with a blood ketone meter if you have one. Urine strips change color and you compare the result to a chart on the packaging. If ketones are moderate or high, contact your doctor or go to an emergency room. Do not exercise, as it can worsen ketone production when levels are already elevated.
Recognize the Symptoms
Mild to moderate high blood sugar often shows up as increased thirst, frequent urination, headache, and blurred vision. These are your body’s early signals that glucose is building up. You might also feel unusually hungry despite eating recently.
If blood sugar stays elevated over days or weeks, the signs shift. Fatigue, unexplained weight loss, slow-healing cuts, recurring skin infections, and yeast infections all point to prolonged hyperglycemia that needs medical attention.
DKA symptoms are more urgent and distinct: nausea, vomiting, abdominal pain, fruity-smelling breath, rapid heartbeat, confusion, and deep labored breathing. If you or someone around you notices these, that’s an emergency room situation, not a wait-and-see one.
Know What Pushed It Up
Food is the obvious trigger, but plenty of non-food factors spike blood sugar in ways that catch people off guard. The CDC lists several that are worth knowing about:
- Poor sleep. Even one night of too little sleep can make your body use insulin less effectively the next day.
- Stress and pain. Physical stress, including something as simple as a sunburn, triggers cortisol release, which raises blood sugar.
- The dawn phenomenon. Hormones naturally surge in the early morning hours, causing blood sugar to rise before you’ve eaten anything. This affects people with and without diabetes, but the spike is harder to manage with diabetes.
- Caffeine. Black coffee with no sugar can still raise blood sugar in some people.
- Dehydration. As mentioned above, less water means more concentrated blood sugar.
- Illness and infection. Your body releases stress hormones to fight infection, which pushes glucose up. Gum disease is a commonly overlooked culprit.
- Certain medications. Some nasal sprays contain chemicals that signal your liver to release more glucose. Steroids are another well-known trigger.
Understanding your personal triggers helps you prevent the next spike, not just react to this one. If you notice patterns (high readings every morning, or after stressful days), that’s useful information to bring to your doctor.
Choose the Right Foods Going Forward
When your blood sugar is already high, the last thing you want is a snack that adds more fast-absorbing carbs. Focus on protein, healthy fat, and fiber, all of which slow glucose absorption and help stabilize levels rather than spike them further.
A small handful of almonds, walnuts, or pistachios (about 1.5 ounces) gives you fiber and fat with very few carbs. A quarter cup of cottage cheese with some berries, a hard-boiled egg, or a third cup of hummus with raw vegetables are all solid choices. Plain low-fat yogurt with fresh fruit works well too. Even three cups of air-popped popcorn is a surprisingly low-carb option. The common thread is avoiding refined carbs and pairing any carbs you do eat with protein or fat to slow digestion.
This isn’t the time for bread, crackers on their own, cereal, or fruit juice. Those will push your numbers higher before they come back down.
When High Blood Sugar Is an Emergency
There’s no single universally agreed-upon cutoff for “go to the ER now.” Clinical guidelines have used thresholds ranging from 300 to 400 mg/dL to define severe hyperglycemia. As a practical rule, a reading above 300 mg/dL that doesn’t come down with your usual correction methods deserves a call to your doctor or a trip to urgent care. If you’re above 300 and showing DKA symptoms (vomiting, confusion, fruity breath, rapid breathing), go to the emergency room.
Persistent readings above 180 mg/dL checked on two separate occasions are the clinical threshold at which insulin therapy is typically started or adjusted. If you’re not on insulin and you’re consistently seeing numbers in this range, that’s a conversation worth having with your provider sooner rather than later.