If your blood glucose is running high, the most important first steps are drinking water, moving your body (if it’s safe to do so), and checking whether ketones are present. What counts as “high” depends on timing: the American Diabetes Association recommends fasting levels between 80 and 130 mg/dL, and readings under 180 mg/dL one to two hours after eating. Anything consistently above those targets needs attention, and anything above 240 mg/dL calls for a ketone check before you do anything else.
Know Your Numbers and What They Mean
A single high reading doesn’t necessarily signal danger. Blood sugar fluctuates throughout the day based on food, stress, sleep, illness, and physical activity. A post-meal spike that settles back down within a couple of hours is very different from a fasting reading that stays elevated morning after morning.
The key thresholds to keep in mind:
- Above 180 mg/dL after meals: Higher than recommended. Worth addressing with the steps below.
- Above 240 mg/dL: Test your urine or blood for ketones before exercising or making other changes.
- Above 270 mg/dL: This is a caution zone. Your blood sugar may be too high to exercise safely.
Drink Water First
When blood sugar is elevated, your kidneys work harder to filter out the excess glucose, pulling extra fluid from your body in the process. That’s why increased thirst and frequent urination are two of the earliest signs of high blood sugar. Drinking water helps your kidneys flush glucose out through urine and prevents the dehydration that high glucose causes on its own. Plain water is ideal. Avoid juice, regular soda, or sweetened drinks that will push your levels higher.
Move Your Body (With One Important Exception)
Physical activity is one of the fastest ways to bring blood sugar down because working muscles pull glucose out of the bloodstream for fuel. Even a 15 to 20 minute walk after a meal can make a noticeable difference. The general recommendation for adults is at least 150 minutes per week of moderate to vigorous aerobic activity, but in the moment, any movement helps.
The exception: if your blood sugar is above 240 mg/dL, test for ketones first. Ketones are acids your body produces when it burns fat instead of glucose for energy, and they accumulate when insulin levels are too low. If ketones are present and you exercise anyway, you risk a dangerous condition called diabetic ketoacidosis. Wait until a ketone test comes back negative before working out. Also skip exercise if you’ve needed help recovering from a serious low blood sugar episode in the past 24 hours.
Check for Ketones When Levels Are Very High
Ketone testing is essential any time your glucose climbs above 240 mg/dL. You can use over-the-counter urine test strips or a blood ketone meter. Blood meters give more precise numbers:
- Below 0.6 mmol/L: Normal range. No immediate concern.
- 0.6 to 1.5 mmol/L: Early warning. This may indicate the start of a problem that needs medical attention.
- Above 1.5 mmol/L: You’re at risk for diabetic ketoacidosis. Contact your diabetes care team immediately.
Untreated high blood sugar combined with positive ketones can escalate quickly. If you develop nausea, vomiting, abdominal pain, fruity-smelling breath, rapid heartbeat, or confusion, those are signs of ketoacidosis and you need emergency care.
Choose the Right Foods Going Forward
When your blood sugar is already elevated, what you eat next matters. The goal is to avoid adding more fast-digesting carbohydrates on top of an already high reading. Reach for foods that are high in protein, healthy fat, or fiber, all of which slow glucose absorption.
Good options include a small handful of almonds or walnuts (about 1.5 ounces), a piece of string cheese, a hard-boiled egg, a third of a cup of hummus with raw vegetables, or plain yogurt without added sugar. Three cups of air-popped popcorn is another surprisingly low-carb choice. The common thread is that these foods won’t trigger another glucose spike while your body works to bring levels back down.
If you’re choosing a full meal rather than a snack, build it around non-starchy vegetables, a lean protein source, and a small portion of whole grains rather than refined carbs. White bread, white rice, sugary cereals, and sweetened beverages are the biggest offenders for pushing blood sugar higher, faster.
Be Careful With Insulin Corrections
If you take insulin and your reading is high, it’s tempting to dose again quickly. But “insulin stacking,” giving a correction dose within three hours of a previous one, is a common cause of dangerous low blood sugar. Rapid-acting insulin stays active in your body for several hours, so a second correction before the first dose has finished working can send your glucose crashing.
Check the timing of your last dose before correcting again. If it’s been less than three hours, wait and recheck. If you’re unsure how to adjust your insulin when readings are persistently high, that’s a conversation to have with your care team so you have a clear plan in advance.
Recognize the Symptoms at Each Stage
High blood sugar doesn’t always announce itself dramatically. Early symptoms tend to be mild enough that people dismiss them: increased thirst, more frequent urination, headache, and blurred vision. These can develop gradually, especially if your glucose has been creeping up over days or weeks.
When blood sugar stays elevated over a longer period, the signs shift. Persistent fatigue, unexplained weight loss, slow-healing cuts, recurring skin infections, and frequent yeast infections all point to chronically high glucose. These symptoms suggest the problem isn’t a one-time spike but an ongoing pattern that needs a treatment adjustment.
The most serious stage is ketoacidosis, which typically develops more rapidly in people with type 1 diabetes but can occur in type 2 as well. Warning signs include nausea and vomiting, stomach pain, deep labored breathing, a fruity odor on the breath, and confusion. Ketoacidosis is a medical emergency.
Track Patterns, Not Just Single Readings
A single high reading tells you what’s happening right now. A pattern of high readings tells you something needs to change. After bringing your glucose down in the short term, pay attention to when spikes tend to happen. Is it consistently high in the morning? After certain meals? During stressful periods or when you’re sleeping poorly?
Log your readings alongside what you ate, how much you moved, and how you slept. Even a few days of this kind of tracking reveals patterns that are invisible from a single number. If your blood sugar is frequently running above target despite following your treatment plan, that’s a signal your plan may need adjusting, whether that means a medication change, a dietary shift, or a different approach to activity.