If your blood sugar is high, the most important first steps are to hydrate, check whether you missed a medication dose, and avoid eating more carbohydrates until your levels start coming down. For most people with diabetes, a reading above 180 mg/dL after meals or above 130 mg/dL while fasting counts as hyperglycemia. What you do next depends on how high the number is and what symptoms you’re experiencing.
Drink Water First
Water helps your kidneys flush excess glucose out through urine. When you’re running high, your body is already pulling water from tissues to dilute the sugar in your blood, which is why you feel thirsty and urinate more often. Drinking water accelerates that process and prevents dehydration from making things worse. Aim for a full glass right away and keep sipping steadily. Stick to plain water or unsweetened beverages, not juice or sports drinks that add more sugar to the problem.
Check Your Medication
The most common reason for an unexpected spike is a missed or mistimed dose of insulin or other glucose-lowering medication. If you use insulin and have a correction dose prescribed by your care team, this is when to use it. Your correction factor tells you how much one unit of insulin will lower your blood sugar, and it’s calculated based on your total daily insulin dose. If you don’t already know your correction factor, that’s a conversation to have with your provider before the next spike happens.
One important timing detail: rapid-acting insulin takes 30 to 60 minutes to start lowering glucose, and it stays active in your body for about four hours. That means you should wait at least two hours after a correction dose before deciding it didn’t work. Taking more insulin too soon, sometimes called “stacking,” can send you crashing into low blood sugar hours later.
Know When Exercise Helps and When It Doesn’t
Light physical activity like a 15-minute walk can lower blood sugar by helping your muscles absorb glucose. For moderate highs, this is one of the fastest non-medication tools you have. But there’s an important cutoff: if your blood sugar is above 270 mg/dL, exercise can actually make things worse.
At that level, your body may not have enough insulin circulating to let glucose into cells. Exercise under those conditions pushes your liver to release even more sugar, and your body starts burning fat for fuel in a way that produces ketones. Before exercising with a reading above 270, test your urine for ketones using an over-the-counter test strip. If ketones are present, skip the workout entirely and focus on hydration and your correction dose instead. Wait until ketones clear before getting active.
Choose the Right Foods
When your blood sugar is elevated, the goal is to stop adding fuel to the fire. Avoid refined carbohydrates, sugary snacks, white bread, and anything that will spike you further. If you need to eat, focus on foods that are high in fiber, protein, and healthy fats, all of which slow glucose absorption and help stabilize levels.
Good options during a high reading include dark leafy greens like spinach or kale, a handful of nuts (walnuts, almonds), half an avocado, or a serving of beans or lentils. These foods are low in simple carbohydrates but rich in fiber and nutrients that support blood sugar regulation. Berries are one of the better fruit choices because they pack fiber alongside their natural sugars. If you’re reaching for grains, whole options like oats, quinoa, or barley are far better than anything made with white flour.
Fatty fish like salmon, sardines, and mackerel provide protein without carbohydrates and deliver omega-3 fatty acids that support cardiovascular health, which matters long-term when you’re managing blood sugar.
Understand Why You Spiked
Food is the obvious culprit, but plenty of non-dietary factors drive blood sugar up. Knowing the cause helps you prevent the next episode.
- Illness or infection. Even a common cold raises blood sugar. Your body releases stress hormones to fight off the infection, and those hormones trigger your liver to dump stored glucose into your bloodstream. Surgery and injuries do the same thing.
- Emotional or physical stress. A bad night’s sleep, a stressful day at work, or intense anxiety all trigger the same hormonal response as illness. Cortisol and adrenaline directly raise blood sugar even if you haven’t eaten anything unusual.
- Medications. Steroids are one of the most common offenders. Prednisone and similar drugs prescribed for inflammation, asthma, or autoimmune conditions can send glucose soaring. If you’ve recently started a new medication and notice higher readings, bring it up with your prescriber.
- Sleep deprivation. Even a single night of poor sleep measurably increases insulin resistance the next day. People who regularly sleep fewer than six hours a night have a significantly elevated risk of developing diabetes. And catching up on the weekend may not fully repair the damage: research shows two nights of recovery sleep isn’t always enough to restore normal glucose control.
If You Use a Continuous Glucose Monitor
A CGM high alert is useful, but it requires a measured response. When the alarm goes off, run through a quick mental checklist: Did you miss an insulin dose? Was your mealtime dose too small for what you ate? Could stress or illness be a factor? For pump users, is there an infusion set problem?
One common mistake is setting high alerts at levels you routinely hit after meals. Post-meal rises are normal, and if your alarm fires every time you eat, you’re more likely to over-correct and end up low. A better approach is setting alerts to catch genuinely elevated readings, not your typical post-meal peak. If you’re new to CGM, many clinicians recommend leaving the high alert off for the first few days while you learn your patterns, then gradually adjusting it as your levels improve.
Warning Signs That Need Emergency Attention
Most high blood sugar episodes resolve with hydration, correction doses, and time. But two serious complications can develop if hyperglycemia goes unchecked, and both require emergency care.
The first is diabetic ketoacidosis, or DKA. This happens when blood sugar climbs above 250 mg/dL and your body, starved for usable glucose, starts breaking down fat so aggressively that acidic ketones build up in your blood. Symptoms include nausea, vomiting, abdominal pain, breath that smells fruity, rapid or labored breathing, and shortness of breath. DKA is most common in type 1 diabetes but can occur in type 2 as well. It is life-threatening without treatment.
The second is hyperosmolar hyperglycemic state, which typically involves blood sugar above 600 mg/dL. At that level, the blood becomes extremely concentrated, and the hallmark symptom is a profound change in mental status: confusion, stupor, or even coma. This condition is more common in type 2 diabetes and in older adults who may not recognize how high their sugar has climbed.
Both conditions share earlier warning signs you can catch: excessive thirst, frequent urination, dry mouth, poor skin turgor (when you pinch the skin on the back of your hand and it’s slow to flatten), and rapid heart rate. If you’re experiencing any combination of these along with a very high reading, fruity breath, vomiting, or confusion, that’s not a wait-and-see situation.
Building a Pattern That Prevents Spikes
Dealing with high blood sugar in the moment is important, but the bigger win is having fewer episodes in the first place. The most impactful daily habits are consistent meal timing, prioritizing fiber and protein at every meal, staying physically active, and protecting your sleep. Extending sleep duration to more than six hours per night has been shown to directly improve glucose tolerance in people who were previously sleep-deprived.
Keeping a simple log of your readings alongside what you ate, how you slept, and what your stress level looked like can reveal patterns that blood sugar numbers alone won’t show. Many people discover that their worst spikes aren’t from the foods they expect, but from stress, poor sleep, or a medication interaction they hadn’t connected to their glucose levels.