A blood sugar reading over 200 mg/dL means you need to take action, but how urgently depends on your symptoms, whether ketones are present, and how long the reading persists. For most people with diabetes, a single reading above 200 can be brought down at home with hydration, medication adjustments, and monitoring. Readings above 240 mg/dL require a ketone check, and certain warning signs call for emergency care.
Step One: Drink Water and Recheck
When your blood sugar is over 200, your kidneys are working to flush excess glucose through urine, which pulls water out of your body. Drinking water helps your kidneys do this job and prevents the dehydration that makes high blood sugar worse. Aim for at least a full glass right away and keep sipping steadily. Research tracking over 3,600 adults found that people who drank less than half a liter of water per day had a significantly higher risk of developing chronic high blood sugar compared to those drinking more.
Recheck your blood sugar after about 15 to 30 minutes if you’ve taken a correction dose of rapid-acting insulin, or after an hour or two if you’re relying on hydration and oral medication. The goal is to see the number trending downward, not necessarily back to normal immediately.
Check for Ketones Above 240 mg/dL
If your reading is 240 mg/dL or higher, test your urine for ketones using an over-the-counter test kit available at most pharmacies. Ketones are acids your body produces when it starts burning fat instead of glucose for energy, a sign that your cells aren’t getting enough insulin. This is especially important if you have type 1 diabetes, but it applies to anyone with a reading that high.
A positive ketone test changes what you should do next. If ketones are present, do not exercise. Physical activity when ketones are elevated can push your blood sugar even higher and accelerate the buildup of acid in your blood. Contact your healthcare provider to discuss how to safely bring your levels down, which typically involves an insulin adjustment rather than physical activity.
Take Your Medication or a Correction Dose
If you use insulin, you may already have instructions from your provider for a correction dose. The general principle is straightforward: one unit of rapid-acting insulin lowers blood sugar by roughly 50 mg/dL in most people, though individual sensitivity ranges widely, from 15 to 100 mg/dL per unit. So if your target is 120 mg/dL and you’re reading 220, you’d need about 2 units as a correction. Your provider should give you a personalized correction factor based on your total daily insulin dose.
If you take oral diabetes medication rather than insulin, make sure you haven’t missed a dose. Taking a missed dose now can help, but don’t double up without guidance. If you’re already taking your medication as prescribed and still seeing readings over 200 regularly, that’s a sign your treatment plan may need adjusting.
When Exercise Helps and When It Doesn’t
Light to moderate physical activity, like a 15-minute walk, is one of the most effective ways to bring down blood sugar in the moment. Your muscles pull glucose from the bloodstream for fuel, which can lower your reading noticeably within 30 to 60 minutes.
There are clear limits, though. The American Diabetes Association recommends against intense exercise when blood sugar is above 250 mg/dL because vigorous activity can temporarily spike glucose even higher. At 350 mg/dL or above, avoid exercise entirely until levels come down. And at any level, if a ketone test comes back moderate or large, skip the workout. Exercise with elevated ketones can worsen a dangerous metabolic spiral.
Why Your Blood Sugar Spiked
Understanding the cause helps you prevent it from happening again. The most common triggers for readings over 200 include:
- Eating more carbohydrates than your medication covers, particularly sugary drinks, large portions of rice or pasta, or frequent snacking
- Illness or infection, including urinary tract infections, flu, COVID-19, or pneumonia. When you’re sick, your body releases stress hormones like cortisol and adrenaline that make cells more resistant to insulin and dump extra glucose into the bloodstream
- Missed or mistimed medication, even by a few hours for some insulin regimens
- Emotional or physical stress, which triggers the same hormonal response as illness
- Steroid medications like prednisone, which are well known for raising blood sugar, sometimes dramatically
- Reduced physical activity, such as during recovery from surgery or an injury
If you’re sick, expect blood sugar to run higher than usual for the duration of the illness. Check more frequently and stay hydrated. The stress hormone surge that accompanies infection causes insulin resistance, meaning your usual dose of medication may not be enough until you recover.
Warning Signs That Need Emergency Care
A reading over 200 is manageable at home in most cases. But certain symptoms signal that your body is tipping into a dangerous state called diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemic state (HHS), both of which require hospital treatment.
DKA develops when the combination of high blood sugar, high ketones, and rising acid levels overwhelms your body’s ability to compensate. More than half of people with DKA experience nausea, vomiting, and abdominal pain. Breathing may become deep and labored, and your breath may smell fruity due to acetone, a byproduct of ketone breakdown. Confusion or difficulty staying alert is a sign of severe DKA.
HHS tends to develop more slowly, often over days, and involves extremely high blood sugar (frequently well above 600 mg/dL) with severe dehydration. The hallmark is altered mental status: confusion, drowsiness, or unresponsiveness. HHS is more common in people with type 2 diabetes, particularly older adults.
Seek emergency care if you experience any of the following alongside a high reading:
- Vomiting that won’t stop or makes it impossible to keep fluids down
- Confusion, excessive drowsiness, or difficulty staying conscious
- Deep, rapid breathing or fruity-smelling breath
- Moderate or large ketones on a urine test, especially if your blood sugar won’t come down
- Blood sugar that stays above 240 mg/dL despite taking correction doses
Preventing Repeated Highs
A single reading over 200 after a large meal or during illness isn’t unusual. Repeated readings over 200, especially fasting readings or numbers that stay elevated for hours, point to a gap in your management plan. Eating smaller portions, spacing carbohydrates throughout the day, and avoiding sugary drinks are the dietary changes with the most direct impact. If you’re on insulin, your provider can recalculate your correction factor and carbohydrate ratios so your doses better match your needs. If you’re on oral medication alone and consistently running above 200, that conversation about adding or changing medication becomes important.
Keeping a log of your readings alongside what you ate, your activity level, and any stressors helps identify patterns that aren’t obvious in the moment. Many people find that a specific meal, a particular time of day, or a recurring situation is behind most of their spikes.