Drinking water, moving your body, and taking prescribed insulin (if you have it) are the fastest ways to bring down high blood sugar. Most people see a noticeable drop within 15 to 60 minutes depending on the method. If your blood sugar is above 300 mg/dL and you feel nauseous, have fruity-smelling breath, or are struggling to breathe, skip this article and call 911 or go to the emergency room immediately.
Drink Water Right Away
Water is the simplest first step when your blood sugar is running high. Your kidneys filter excess glucose out of your blood and excrete it through urine, but they need adequate hydration to do this efficiently. When you’re dehydrated, your kidneys slow down that filtering process, and glucose accumulates in the bloodstream. Drinking water helps restore that excretion pathway and can bring levels down gradually over the next hour or two.
There’s no single magic number for how much to drink, but sipping steadily over the next couple of hours is more effective than chugging a large amount at once. Aim for a glass every 15 to 30 minutes until you’re urinating regularly. Stick to plain water or unsweetened beverages. Juice, sports drinks, and anything with added sugar will push your levels higher.
Move Your Body
Physical activity pulls glucose out of your bloodstream and into your muscles, where it’s burned for energy. It also makes your cells more responsive to insulin, so any insulin your body produces (or that you’ve injected) works harder. A review of exercise studies found that all forms of activity, including walking, cycling, and resistance training like bodyweight squats, lowered long-term blood sugar markers by an average of 0.7 percentage points in people with diabetes. That improvement held even without weight loss.
For an immediate spike, a brisk 15- to 30-minute walk is often enough to see your numbers start dropping. The best window is one to three hours after eating, when blood sugar tends to peak. Even 10 minutes of movement helps if that’s what you can manage. One important caution: if your blood sugar is above 300 mg/dL and you have ketones in your urine, exercise can actually make things worse. In that situation, focus on hydration and contact your healthcare provider instead.
Use Insulin If You Have It Prescribed
If you’re on a rapid-acting insulin regimen, a correction dose is the most predictable way to lower a high reading. According to the CDC, rapid-acting insulin begins working within about 15 minutes, peaks at around 1 hour, and stays active for 2 to 4 hours. Follow the correction factor your doctor has given you. Taking more than your prescribed dose in an attempt to bring numbers down faster is dangerous and can cause a severe low blood sugar crash.
If you don’t use insulin, your prescribed oral medications still play a role, but they work on a slower timeline. Don’t double up on doses to compensate for a high reading.
Manage Stress, Which Quietly Raises Glucose
Stress is one of the most overlooked causes of high blood sugar. When you’re stressed, your body treats it like a physical emergency: insulin levels drop, adrenaline and cortisol rise, and your liver dumps stored glucose into the bloodstream to fuel a fight-or-flight response. At the same time, cortisol makes your muscle and fat cells less responsive to insulin. The result is a blood sugar spike that has nothing to do with what you ate.
If you’re dealing with a stubborn high reading and you’re also anxious, angry, or under pressure, addressing the stress can help. Deep breathing exercises, where you inhale for 4 counts, hold for 4, and exhale for 6 to 8, activate your body’s calming nervous system response. Even 5 minutes of slow, controlled breathing can start reversing that hormonal cascade. Other options include stepping outside for fresh air, doing a short meditation, or simply lying down in a quiet room.
Eat Fiber at Your Next Meal
Once you’ve addressed the immediate spike, what you eat next matters. Soluble fiber slows the rate at which sugar enters your bloodstream after a meal, preventing another sharp rise. A meta-analysis found that people with type 2 diabetes who consumed about 13 grams of soluble fiber per day (roughly one tablespoon of a fiber supplement like psyllium husk) lowered their long-term blood sugar marker by about 0.6 percentage points. That’s a meaningful shift from a single dietary change.
Good whole-food sources of soluble fiber include oats, beans, lentils, flaxseed, avocados, and Brussels sprouts. Pairing these with protein and healthy fat at meals creates a slower, flatter blood sugar curve compared to eating carbohydrates on their own. If your blood sugar is high right now, avoid refined carbs like white bread, crackers, or sugary snacks for your next meal entirely.
Apple Cider Vinegar: A Modest Helper
Apple cider vinegar has some legitimate evidence behind it, though the effect is moderate. In a randomized clinical trial, people with diabetes who consumed about 2 tablespoons (30 ml) of apple cider vinegar daily for eight weeks saw their fasting blood sugar drop by an average of 23 mg/dL and their long-term blood sugar marker fall by about 1.4 percentage points. The control group saw no significant change.
This isn’t a quick fix for an acute spike, but it can be a useful daily habit. Dilute it in a full glass of water to protect your tooth enamel and stomach lining. Drinking it before or with a carb-heavy meal may help blunt the post-meal glucose rise.
When High Blood Sugar Is an Emergency
Most high blood sugar episodes are uncomfortable but manageable at home. Some are not. The CDC identifies these as signs of diabetic ketoacidosis, a life-threatening condition that requires emergency care:
- Blood sugar at or above 300 mg/dL that won’t come down
- Fruity-smelling breath
- Persistent vomiting or inability to keep fluids down
- Difficulty breathing
- High ketone levels on a urine or blood ketone test
Ketoacidosis develops when your body can’t get glucose into cells and starts breaking down fat at a dangerous rate, producing acidic compounds called ketones. It’s most common in type 1 diabetes but can occur in type 2 as well. If you have multiple symptoms from the list above, don’t wait to see if things improve. Call 911 or get to an emergency room.