If your blood sugar is high, the most important immediate steps are to hydrate, check for ketones if you’re above 200 mg/dL, and avoid foods that will push it higher. What you do next depends on how high the reading is and whether you’re already managing diabetes with medication. Here’s a practical walkthrough of how to bring it down and when to get help.
Drink Water First
Water is your fastest passive tool for lowering blood sugar. When glucose levels are elevated, your kidneys work to filter the excess sugar out through urine. That process pulls water along with it, which is why high blood sugar makes you urinate more and feel thirsty. Drinking water supports your kidneys in clearing that glucose and prevents dehydration from making the situation worse.
There’s no single magic number for how much to drink, but steady sipping over the next hour or two is more effective than gulping a large amount at once. Stick to plain water or unsweetened beverages. Juice, regular soda, or sports drinks will add sugar you don’t need right now.
Check for Ketones Above 200 mg/dL
If your blood sugar is over 200 mg/dL, test your urine or blood for ketones. Ketones are acids your body produces when it starts burning fat for fuel instead of glucose, and they build up when insulin levels are too low. You can pick up ketone test strips at most pharmacies without a prescription.
This step matters because ketones at high levels can lead to diabetic ketoacidosis (DKA), a serious and potentially life-threatening condition. DKA is most common in people with type 1 diabetes but can happen with type 2 as well. If ketones are present, do not exercise (more on that below), and focus on hydration and following your prescribed insulin plan.
When to Call 911
Certain combinations of symptoms signal a medical emergency. Go to the emergency room or call 911 if:
- Your blood sugar stays at 300 mg/dL or above and won’t come down
- Your breath smells fruity
- You’re vomiting and can’t keep food or drinks down
- You’re having trouble breathing
- You have multiple signs of DKA at the same time
High ketones combined with any of these symptoms mean your body’s chemistry is shifting in a dangerous direction. Don’t wait to see if it improves on its own.
Use Your Correction Insulin if Prescribed
If you take insulin and your doctor has given you a correction factor, this is when to use it. The basic formula is: take the difference between your current blood sugar and your target number, then divide by your correction factor. That tells you how many extra units to take.
For example, if your blood sugar is 280, your target is 120, and your correction factor is 40, you’d calculate (280 – 120) รท 40 = 4 units. Your specific numbers should come from your care team, because correction factors vary widely from person to person. If you haven’t been given a correction dose plan, don’t guess. Call your doctor’s office instead.
If you take oral diabetes medications rather than insulin, you typically can’t add an extra dose to bring a spike down. Focus on hydration, food choices, and gentle movement while the medication you’ve already taken continues working.
Why Exercise Helps, and When It Doesn’t
Physical activity pulls glucose out of your bloodstream and into your muscles, which can lower blood sugar noticeably within 15 to 30 minutes. A brisk walk is usually enough. You don’t need an intense workout.
However, there’s an important cutoff. If your blood sugar is above 270 mg/dL, exercise enters a caution zone. At that level, test for ketones before doing anything active. If ketones are present, exercising can actually make things worse by triggering ketoacidosis. Wait until your ketone test comes back clear before you lace up your shoes. Bring your blood sugar down with hydration and insulin first, then use movement as a follow-up tool.
What to Eat (and What to Skip)
When your blood sugar is already elevated, the last thing you want is a meal that sends it higher. That doesn’t mean you should skip eating entirely, but it does mean choosing carefully.
Focus on non-starchy vegetables like broccoli, spinach, and green beans. These have minimal impact on blood sugar. Avoid refined carbohydrates like white bread, white rice, pasta, and anything with added sugar. If you do eat carbs, pair them with protein, fat, or fiber. That combination slows digestion and prevents the sharp rise that simple carbs cause on their own.
This isn’t just advice for a single spike. Eating roughly the same amount of carbohydrates at each meal helps keep blood sugar more predictable day to day. If you’re not sure how many grams of carbs to aim for per meal, a registered dietitian can help you set a target based on your medications, activity level, and goals.
When to Contact Your Doctor
Not every high reading requires a phone call, but patterns do. Contact your doctor if your blood sugar stays higher than your target for two or three days and you can’t identify why. Also call if a reading hits 300 mg/dL and nothing you’re doing is bringing it down. These situations suggest something has changed, whether it’s a medication that needs adjusting, an illness affecting your levels, or a lifestyle factor you haven’t identified yet.
If you’re seeing frequent spikes but haven’t been diagnosed with diabetes, a single high reading from a home monitor isn’t a diagnosis. Your doctor will likely order a fasting glucose test or an A1C test, which measures your average blood sugar over the past two to three months. For most adults with diabetes, clinical guidelines recommend targeting an A1C of 6.5% or lower, though your doctor may set a less strict goal of 7% to 8% depending on your age, health history, and risk of low blood sugar episodes.
Preventing the Next Spike
Once you’ve brought a high reading down, it’s worth looking at what caused it. Common triggers include eating more carbohydrates than usual, missing a medication dose, stress, illness, poor sleep, and dehydration. Even something as simple as the timing of a meal relative to your medication can make a difference.
Tracking your blood sugar alongside what you eat, when you take medication, and how active you were can reveal patterns that aren’t obvious in the moment. Many people notice, for instance, that certain meals spike their blood sugar more than others, or that readings run higher on days they skip their morning walk. These patterns give you concrete things to adjust rather than trying to manage blood sugar by feel alone.