If your blood sugar is too high, the most important immediate steps are drinking water, taking your prescribed medication if you haven’t already, and monitoring your levels closely. Most mild to moderate spikes can be managed at home, but blood sugar that stays above 300 mg/dL after repeated checks is a medical emergency.
Drink Water First
Water is the single most effective thing you can reach for right now. When blood sugar rises, your blood becomes more concentrated with glucose. Your kidneys respond by producing more urine to filter it out, which pulls even more water from your body. This creates a cycle: dehydration makes your blood sugar reading climb higher, and higher blood sugar causes more dehydration.
Plain water is the best choice. Sugar-free fluids also work. The goal is to give your kidneys enough fluid to flush excess glucose through urination. Sip steadily rather than forcing large amounts at once. Avoid juice, regular soda, or sports drinks with sugar, as these will push your levels higher.
Check Your Medication
If you take insulin or another glucose-lowering medication, think about whether you missed or delayed a dose. A skipped dose is one of the most common reasons for a sudden spike. Take your medication as prescribed if you’re overdue.
If you use rapid-acting insulin with a correction factor your doctor has given you, you can calculate a correction dose. The general principle is that one unit of rapid-acting insulin lowers blood sugar by about 50 mg/dL, though this varies widely between individuals, ranging from 15 to over 100 mg/dL per unit. Use whatever correction factor your care team established for you, not a guess. Taking extra insulin without knowing your personal ratio risks a dangerous low later.
If you don’t have access to your medications, eat as few carbohydrates as possible until you can get them. This is especially critical for people with type 1 diabetes who are without insulin. In emergencies, pharmacies may be able to provide medication without a prescription.
Move Your Body (With One Important Caveat)
Light physical activity, like a 15-minute walk, helps your muscles pull glucose out of your bloodstream for energy. This can noticeably lower your numbers within 30 to 60 minutes. But there’s a safety check you need to do first.
If your blood sugar is very high, test for ketones before exercising. You can do this with urine ketone strips available at most pharmacies. If the result shows moderate or high ketones, do not exercise. Physical activity when ketones are present can make things significantly worse. If your ketone test is negative and you feel well, light movement is safe and helpful.
Identify What Caused the Spike
Understanding what pushed your sugar up helps you prevent it from happening again. Some triggers are obvious, like a high-carb meal. Others are surprisingly easy to miss.
- Illness or infection: Even a mild cold triggers stress hormones that raise blood sugar. You may need to check levels more frequently when you’re sick.
- Poor sleep: A single night of inadequate sleep makes your body use insulin less efficiently the next day.
- Skipping breakfast: Going without a morning meal can cause higher blood sugar readings after both lunch and dinner.
- Stress or pain: Physical stress counts too. Even sunburn can spike your levels because pain triggers a stress response.
- Dehydration: Less water in your body means glucose is more concentrated in your blood, producing a higher reading even if you haven’t eaten anything unusual.
- Certain medications: Some nasal decongestant sprays contain chemicals that signal your liver to release more glucose. Steroids are another common culprit.
Know When to Check for Ketones
Ketones are acids your body produces when it burns fat instead of glucose for energy. Small amounts are normal, but when blood sugar is high and your body can’t use that glucose properly (typically due to insufficient insulin), ketone levels can climb to dangerous territory. This is the beginning of diabetic ketoacidosis, or DKA, which is life-threatening if untreated.
Test your urine for ketones any time your blood sugar is above 240 to 300 mg/dL, especially if you have type 1 diabetes. The test strips change color to indicate a small, moderate, or high level. A small result warrants retesting in a few hours and extra hydration. Moderate or high ketones mean you should contact your diabetes care team immediately.
When High Blood Sugar Is an Emergency
Get emergency medical help if your blood sugar reads above 300 mg/dL on more than one test and isn’t coming down with your usual management. You should also seek immediate care if you have ketones in your urine and can’t reach your healthcare provider.
Watch for these specific warning signs of DKA or a related crisis called hyperosmolar hyperglycemic state:
- Extreme thirst that doesn’t go away with drinking
- Urinating far more frequently than normal
- Nausea, vomiting, or abdominal pain
- Shortness of breath
- A fruity or acetone-like smell on your breath
- Confusion, difficulty concentrating, or unusual drowsiness
- Weakness or fatigue that feels different from your baseline
These symptoms can escalate quickly. DKA is treated in a hospital with IV fluids, insulin, and electrolyte replacement. Most people recover well with prompt treatment, but delays make the situation significantly more dangerous.
Preventing the Next Spike
A single high reading isn’t a crisis in most cases. It’s a signal. If spikes keep happening, the pattern matters more than any individual number. Keep a simple log of your readings alongside what you ate, how you slept, your stress level, and whether you were sick or took any new medications. Even a week of tracking often reveals a pattern that’s easy to fix once you see it.
Staying consistently hydrated throughout the day, not just during a spike, helps your kidneys manage glucose more effectively and prevents the dehydration cycle from amplifying smaller rises. Eating meals on a regular schedule, particularly breakfast, and getting enough sleep are two of the most underrated tools for keeping levels stable. These aren’t dramatic interventions, but over time they reduce both the frequency and severity of high blood sugar episodes.