When your blood sugar is high, the first steps are to hydrate with water, check for ketones if your reading is above 240 mg/dL, and avoid eating additional carbohydrates until your levels come down. How urgently you need to act depends on how high the number is and what symptoms you’re experiencing.
A single high reading isn’t always cause for alarm, but knowing which actions to take at different thresholds can prevent a mild spike from becoming a dangerous one.
First Steps to Bring Blood Sugar Down
Start drinking water immediately. Water helps your kidneys flush excess glucose through urine, and dehydration makes high blood sugar worse. Stick to zero-calorie fluids like water or unsweetened tea. Avoid juice, regular soda, or sports drinks, which will push your levels higher.
If you take rapid-acting or mealtime insulin, follow the correction dose your provider has prescribed. Don’t guess at a dose if you haven’t been given specific instructions for corrections. If you’re on long-acting insulin, continue taking it as scheduled.
Light physical activity, like a 15-minute walk, can help your muscles pull glucose out of your bloodstream. But there’s an important exception: 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 use the glucose, and physical activity can trigger your liver to release even more. Test for ketones before working out if you’re in that range.
Check for Ketones Above 240 mg/dL
When blood sugar climbs above 240 mg/dL, your body may start breaking down fat for energy instead of glucose. This process produces ketones, acidic byproducts that can accumulate to dangerous levels. You can check for ketones with an over-the-counter urine test strip available at most pharmacies.
If the test comes back positive, your body has started the chemical shift that can lead to diabetic ketoacidosis (DKA), a life-threatening condition. Contact your provider to discuss how to lower your blood sugar safely. Do not exercise until a follow-up test shows ketones are no longer present.
When High Blood Sugar Is an Emergency
Certain signs mean you should call 911 or go to the emergency room immediately:
- Blood sugar stays at 300 mg/dL or above and isn’t responding to your usual correction plan
- Fruity-smelling breath, a hallmark sign that ketones have built up significantly
- Vomiting that prevents you from keeping food or fluids down
- Difficulty breathing or rapid, labored breaths
- Confusion or extreme fatigue
These are symptoms of DKA. It develops quickly, sometimes within hours, and requires emergency treatment. Don’t wait to see if things improve on their own if multiple symptoms are present.
Common Triggers for Blood Sugar Spikes
Understanding why your blood sugar spiked helps you prevent it from happening again. Some causes are obvious: eating more carbohydrates than expected, missing a dose of medication, or being less active than usual. Others are less intuitive.
Stress is one of the most common hidden triggers. When you’re stressed, your body releases hormones that tell your liver to dump stored glucose into your bloodstream, a survival mechanism that works against you when you have diabetes. Physical stress counts too. Something as simple as a sunburn causes enough pain-related stress to raise blood sugar.
The “dawn phenomenon” catches many people off guard. Hormones that naturally surge in the early morning hours (typically between 4 and 8 a.m.) can cause fasting blood sugar to be higher than expected, even if you ate well the night before. If you’re consistently seeing high morning numbers, this is a pattern worth discussing with your provider.
Even certain over-the-counter products can play a role. Some nasal decongestant sprays contain chemicals that stimulate your liver to produce more glucose. If you’re fighting a cold and notice unexplained spikes, your cold medicine could be a factor.
After the Spike: Monitoring and Follow-Up
Once you’ve taken steps to bring your blood sugar down, recheck your levels within one to two hours to confirm the trend is moving in the right direction. If you tested positive for ketones earlier, retest those as well before resuming exercise or your normal routine.
A single spike doesn’t necessarily mean your treatment plan needs to change. But if high readings are becoming a pattern, your provider may adjust the dosage or timing of your medication. One useful benchmark: an A1C test measures your average blood sugar over the past two to three months. If your A1C is above 7%, your blood sugar has been running above a healthy range on average, and a treatment adjustment is likely warranted.
Keep a log of your high readings along with what you ate, your activity level, stress, and any illness or unusual circumstances. This context makes it much easier for your provider to spot patterns and fine-tune your plan rather than making broad changes based on a single number.