High Blood Sugar: Safe Steps to Take and When to Contact a Doctor

What Blood Sugar Level Is Considered High?

There is no single number that is “high” for every person in every situation.

Your target depends on:

• Whether you have type 1, type 2, or gestational diabetes
• Your age
• Pregnancy status
• Your medicine and insulin plan
• Your risk of low blood sugar
• Kidney, heart, liver, or other health conditions
• The time since your last meal
• Whether you use a glucose meter or continuous glucose monitor

For many people using a continuous glucose monitor, a commonly used general target range is 70 to 180 mg/dL, or about 3.9 to 10.0 mmol/L. Your healthcare team may prescribe a different range.

A value above your personal range is a high reading. It does not automatically mean that an emergency is occurring.

Symptoms, ketones, illness, dehydration, pregnancy, and the direction of the glucose trend can be as important as the number itself.

How Do mg/dL and mmol/L Compare?

Blood glucose may be reported in:

• Milligrams per deciliter: mg/dL
• Millimoles per liter: mmol/L

To convert mg/dL to mmol/L, divide by 18.

To convert mmol/L to mg/dL, multiply by 18.

These conversions do not tell you what treatment to take. Use your personal diabetes action plan.

What Are the Symptoms of High Blood Sugar?

Possible early symptoms include:

• Increased thirst
• Frequent urination
• Waking at night to urinate
• Dry mouth
• Fatigue or weakness
• Headache
• Blurred vision
• Difficulty concentrating
• Feeling generally unwell

Symptoms may develop slowly, and some people have no obvious symptoms even when glucose is above target.

More serious symptoms include:

• Nausea or vomiting
• Abdominal pain
• Fast or deep breathing
• Fruity-smelling breath
• Severe dehydration
• Confusion
• Extreme sleepiness
• Collapse

Read High Blood Sugar Warning Signs: Symptoms, Testing, and When It Is Urgent for a separate symptom-focused guide.

What Causes High Blood Sugar?

Common causes include:

• Missing insulin or diabetes medicine
• Taking a smaller dose than prescribed
• An insulin pump, cannula, tubing, or infusion-set problem
• Insulin that has expired, overheated, frozen, or been stored incorrectly
• Eating more carbohydrate than expected
• Illness or infection
• Physical or emotional stress
• Reduced activity
• Some high-intensity exercise
• Steroid medicines
• Other medicines that affect glucose
• Dawn phenomenon
• Hormonal changes
• Dehydration
• Progression of diabetes or changing insulin needs

A high reading after food does not prove that one particular food caused the entire problem.

Repeated high readings should be reviewed with the healthcare team rather than managed through repeated guessing or self-directed dose changes.

High Blood Sugar Safety Table

Should You Check a High Reading Again?

Repeat the test when a finger-stick result is unexpected or does not match how you feel.

For a Finger-Stick Meter

• Wash your hands with soap and water.
• Dry them completely.
• Use a fresh, unexpired test strip.
• Check that the strip container has been stored correctly.
• Use the meter according to the manufacturer’s instructions.

Sugar, fruit, food, lotion, or another substance on the fingers can produce an inaccurate result.

For a Continuous Glucose Monitor

A CGM measures glucose in fluid under the skin rather than directly in blood. There can be a delay when glucose is changing quickly.

Confirm the reading with a finger-stick meter when:

• The CGM result does not match your symptoms
• The sensor displays an error or unusual trend
• Your device instructions require confirmation
• Your treatment plan tells you to confirm before taking a correction

Read Home Diabetes Testing: Glucose Checks, A1C Questions, and When to Seek Care.

Should You Take Extra Insulin or Diabetes Medicine?

Only use extra rapid-acting insulin when your written correction plan tells you:

• Which glucose level requires a correction
• How to calculate the dose
• How long to wait before rechecking
• When another correction is safe
• When to check ketones
• When to call the diabetes team

Taking correction doses too close together can cause insulin stacking, which may lead to dangerous low blood sugar later.

Do not:

• Double a missed tablet dose unless the prescriber specifically instructed this
• Borrow another person’s insulin
• Use a correction formula found online
• Change basal insulin independently
• Stop insulin during illness without urgent professional advice
• Inject more insulin because the first dose does not appear to work immediately

People with type 1 diabetes need insulin to prevent ketone production. Follow the type 1 sick-day instructions provided by the diabetes team.

What if You Use an Insulin Pump?

Unexpectedly high glucose may result from:

• A dislodged cannula
• Bent tubing
• A blocked infusion set
• An empty reservoir
• Air in the tubing
• Damaged insulin
• A pump or sensor communication problem

Follow the pump-failure and ketone instructions supplied by your diabetes service and device manufacturer.

Can Drinking Water Lower High Blood Sugar?

Water helps replace fluid lost through frequent urination and can reduce the risk of worsening dehydration.

However, water is not an emergency glucose-lowering treatment and does not replace:

• Insulin
• Prescribed medication
• Ketone checks
• A sick-day plan
• Professional medical care

Choose plain water or another sugar-free drink when you are able to drink safely.

Do not force large amounts of fluid if you:

• Have heart failure
• Have advanced kidney disease
• Have been prescribed a fluid restriction
• Are vomiting repeatedly
• Have difficulty swallowing

Follow individualized hydration advice from your medical team.

What Should You Eat When Blood Sugar Is High?

No food reliably lowers an active high glucose reading immediately.

Eating nuts, eggs, avocado, cinnamon, vinegar, or another food is not a substitute for prescribed treatment.

General steps may include:

• Avoid sugar-sweetened drinks
• Avoid adding an unplanned large carbohydrate portion
• Follow the meal plan connected to your insulin or medicine schedule
• Choose balanced portions when you can eat normally
• Do not skip all food when your medicine must be taken with meals

During illness, nausea, vomiting, pregnancy, or ketone production, food and fluid advice may differ. Follow your sick-day plan.

Does Apple Cider Vinegar Treat High Blood Sugar?

No. Apple cider vinegar is not an acute treatment for hyperglycemia, DKA, or HHS.

It can irritate the mouth, esophagus, and stomach, damage tooth enamel, interact with some medicines, and delay proper treatment if used as a replacement for medical care.

Does Cinnamon Lower Blood Sugar Immediately?

No. Cinnamon should not be presented as a rapid treatment for a high glucose reading.

Do not use cinnamon supplements or concentrated products instead of prescribed diabetes treatment.

Is It Safe to Exercise With High Blood Sugar?

Physical activity can lower glucose in some people by helping muscles use glucose and increasing insulin sensitivity.

However, exercise is not always safe during an acute high reading.

Do Not Exercise When:

• Ketones are present
• You have symptoms of DKA
• You are vomiting
• You are dehydrated
• You have severe abdominal pain
• You feel faint, confused, or extremely weak
• Your diabetes plan tells you not to exercise at that level

Exercise with ketones may cause glucose and ketone levels to rise further.

High-intensity exercise, sprinting, competitive activity, or heavy weight training can temporarily raise glucose because of stress hormones.

When you feel well, have no ketones, and your care plan permits activity, gentle movement may be reasonable. Do not use walking as a substitute for an insulin correction or emergency care.

Read Walking for Health: Benefits and Safety Tips.

When Should You Check for Ketones?

Ketones are chemicals produced when the body breaks down fat because it cannot use enough glucose for energy.

Ketone testing is particularly important for people with type 1 diabetes, but DKA can also occur in type 2 diabetes and in people using certain medicines.

Check ketones according to your written plan when:

• You are sick
• Your glucose remains high despite a correction
• You have nausea, vomiting, or abdominal pain
• You have fruity-smelling breath
• You are breathing more deeply than usual
• An insulin pump may not be delivering insulin
• Your glucose reaches the threshold specified by your team

Current CDC guidance advises ketone testing when a person is sick and glucose is 240 mg/dL, or about 13.3 mmol/L, or higher.

Your personal plan may recommend ketone testing at a different glucose level.

Blood Ketones Versus Urine Ketones

Blood ketone tests measure the current level of beta-hydroxybutyrate and may detect changes sooner.

Urine strips show ketones that have already passed into the urine, so they may lag behind current blood levels.

Follow the instructions for your test device and the action thresholds provided by your healthcare team.

What Is Diabetic Ketoacidosis?

Diabetic ketoacidosis, or DKA, occurs when there is not enough effective insulin and ketones build to dangerous levels, making the blood acidic.

DKA is most common in type 1 diabetes, but it can also occur in type 2 diabetes.

Possible DKA Symptoms

• High glucose, although it is not always extremely high
• High blood or urine ketones
• Thirst
• Frequent urination
• Dry mouth
• Nausea
• Vomiting
• Abdominal pain
• Fast or deep breathing
• Fruity or acetone-like breath
• Fatigue
• Sleepiness
• Confusion

DKA requires urgent hospital treatment with carefully monitored fluids, insulin, electrolytes, and treatment of the cause.

Do not try to treat severe DKA symptoms with water, food, exercise, vinegar, cinnamon, or an unplanned insulin dose.

Can DKA Occur Without Very High Blood Sugar?

Yes. This is sometimes called euglycemic DKA.

It is particularly important for people taking an SGLT2 inhibitor. Medicines in this group include products containing:

• Canagliflozin
• Dapagliflozin
• Empagliflozin
• Ertugliflozin
• Bexagliflozin
• Sotagliflozin

DKA can occur with glucose below the level usually expected for DKA.

Seek urgent medical care for nausea, vomiting, abdominal pain, unusual tiredness, dehydration, or fast breathing when taking an SGLT2 inhibitor, even if glucose is not extremely high.

Do not wait for a home glucose reading to become very high before seeking help.

Follow the medicine-specific sick-day and surgery instructions given by your prescriber. Do not stop or restart prescription medicine without professional guidance unless your written sick-day plan specifically instructs you.

What Is Hyperosmolar Hyperglycemic State?

Hyperosmolar hyperglycemic state, also called hyperosmolar hyperglycaemic state or HHS, is a life-threatening diabetes emergency.

It is more commonly associated with type 2 diabetes.

HHS generally involves:

• Extremely high blood glucose
• Severe dehydration
• Very frequent urination early in the illness
• Intense thirst
• Weakness
• Dry mouth and skin
• Vision changes
• Confusion
• Reduced alertness or unconsciousness

Ketones may be absent or only mildly elevated, which means a negative urine ketone test does not rule out HHS.

HHS requires hospital treatment.

What Is the Difference Between DKA and HHS?

What Should a Diabetes Sick-Day Plan Include?

Illness can raise glucose even when you are eating less.

A written sick-day plan should explain:

• How often to check glucose
• When and how to test ketones
• Which medicines to continue
• Which medicines may need to be paused
• How to use correction insulin
• How much fluid to drink
• What to do when you cannot eat normally
• When to contact the diabetes team
• When to use emergency services

General safety steps include:

• Monitor glucose more often than usual
• Check ketones according to the plan
• Continue insulin unless a qualified clinician directs otherwise
• Use fluids that match your glucose and sick-day instructions
• Record glucose, ketones, medicine, temperature, vomiting, and fluid intake
• Ask for help early if you cannot keep fluids down

Different medicines have different sick-day rules. Do not copy another person’s plan.

When Should You Contact Your Diabetes Team?

Contact your diabetes clinician, endocrinologist, specialist nurse, diabetes educator, GP, family doctor, or primary care clinician when:

• Glucose remains above the action level in your personal plan
• Repeated correction doses are not working
• Ketones are above the level specified in your plan
• You are sick and unsure how to adjust medicine or insulin
• You cannot identify why readings are high
• You suspect a pump or infusion-set problem
• You repeatedly wake with high glucose
• High readings occur at the same time each day
• You have repeated infections
• You are using steroids and glucose is rising
• You are pregnant or may be pregnant
• You have difficulty obtaining insulin, strips, sensors, or ketone supplies

Use emergency services rather than waiting for a routine call-back when severe symptoms are present.

What if You Do Not Have a Diabetes Diagnosis?

A high home glucose result does not diagnose diabetes by itself.

Arrange professional assessment when:

• You have repeated high readings
• You have thirst and frequent urination
• You are losing weight without trying
• You have unexplained fatigue or blurred vision
• You have recurrent infections
• You had high glucose during pregnancy
• You are using steroid medicine
• You have strong diabetes risk factors

Seek urgent help if you have vomiting, abdominal pain, deep breathing, fruity breath, confusion, severe dehydration, or extreme drowsiness.

DKA may be the first sign of previously undiagnosed diabetes.

What Should You Do About High Blood Sugar During Pregnancy?

Pregnancy glucose targets are usually lower than general diabetes targets.

High glucose during pregnancy may affect the pregnant person and baby, so do not apply a nonpregnant adult correction plan unless the maternity diabetes team prescribed it.

Contact the maternity or diabetes team for:

• Repeated readings above the pregnancy target
• Vomiting or inability to eat
• Ketones
• Reduced fetal movement
• Concern about medicine or insulin doses
• Illness, fever, or dehydration

Seek urgent care for DKA symptoms. DKA during pregnancy may occur at lower glucose levels than expected.

Can a Home Glucose Meter Diagnose Diabetes?

No. A home meter or continuous glucose monitor is useful for monitoring, but diabetes diagnosis normally requires professional laboratory testing and clinical interpretation.

Common diagnostic tests include:

• A1C or HbA1c
• Fasting plasma glucose
• Oral glucose tolerance test
• Random plasma glucose when classic symptoms are present

A1C may be less reliable in some situations, including certain anemias, hemoglobin variants, pregnancy, recent blood loss, kidney disease, or blood transfusion.

Can Stress Raise Blood Sugar?

Yes. Physical or emotional stress can increase hormones that signal the liver to release glucose.

Relaxation may support overall diabetes management, but deep breathing does not replace insulin, prescribed medicine, or emergency care.

Read Deep Breathing and Meditation for Stress Management.

How Can Repeated High Blood Sugar Be Prevented?

Long-term prevention depends on identifying the pattern rather than reacting to each reading in isolation.

Helpful topics to review with the healthcare team include:

• Medication timing and adherence
• Insulin-to-carbohydrate ratios
• Correction factors
• Injection technique
• Insulin storage
• Pump and infusion-set technique
• Meal composition and carbohydrate portions
• Physical activity
• Sleep
• Stress
• Illness plans
• Steroid treatment
• Dawn phenomenon
• Menstrual-cycle or hormonal patterns
• CGM alerts and trend settings

Do not change multiple parts of the plan at once without professional guidance. This can make it difficult to identify what helped and may increase the risk of hypoglycemia.

Read How to Keep Diabetes Under Control: Monitoring, Food, Activity, and Medical Care.

What Should You Avoid Doing?

• Do not panic after one unexpected reading.
• Do not assume water will correct severe hyperglycemia.
• Do not take an unplanned insulin dose.
• Do not stack correction doses too closely together.
• Do not double a missed tablet dose without instructions.
• Do not exercise when ketones are present.
• Do not use vinegar, cinnamon, supplements, or detox products as emergency treatment.
• Do not eat a snack to “absorb” or lower high glucose.
• Do not stop insulin during illness without urgent professional advice.
• Do not rely only on glucose when DKA symptoms are present.
• Do not ignore vomiting, deep breathing, confusion, or severe dehydration.
• Do not drive when you are confused, faint, or severely unwell.

How Should You Prepare for a Diabetes Appointment?

Bring or record:

• Glucose-meter or CGM reports
• Dates and times of high readings
• Meal and carbohydrate information
• Medicine and insulin doses
• Ketone results
• Exercise timing
• Illness, infection, stress, or steroid use
• Pump or infusion-set changes
• Episodes of low blood sugar after corrections
• Your questions and concerns

Patterns over several days may be more useful than one isolated number.

What Questions Should You Ask Your Healthcare Team?

• What is my personal target range?
• At what level should I take a correction dose?
• How do I calculate the correction safely?
• How long should I wait before correcting again?
• When should I check ketones?
• What ketone result requires a phone call?
• When should I avoid exercise?
• What are my sick-day medicine instructions?
• Which medicines should never be stopped suddenly?
• What should I do if my insulin pump fails?
• Which symptoms require emergency care?
• What should I do if I cannot keep fluids down?
• How should I manage glucose while taking steroids?
• Could my CGM or meter be giving inaccurate readings?
• Do I need an A1C or another laboratory test?