How long does it take to reduce a reading of 800 to get back to a normal range?




Question:


How long does it take to reduce a blood sugar reading of 800 mg/dL back to a normal range? Is hospitalization necessary?




Emergency Quick Answer


A blood sugar reading of 800 mg/dL is a medical emergency unless it is clearly a meter error that is immediately disproven by repeat testing.


Do not try to bring 800 mg/dL down at home with water, exercise, extra insulin, or home remedies unless you are following a written emergency plan from your doctor.


At this level, hospitalization or emergency department treatment is often necessary because doctors must check for dehydration, ketones, acid level, kidney function, potassium, sodium, infection, diabetic ketoacidosis, or hyperosmolar hyperglycemic state.



Answer by Dr. Albana Greca, MD, MMedSc


Hello,


A blood sugar of 800 mg/dL is far above the safe range. The most important answer is not “how long will it take?” but “you need urgent medical evaluation now.”


How Long Does It Take to Lower 800 mg/dL?


There is no safe fixed time because treatment depends on why the glucose is so high, how dehydrated the person is, whether ketones are present, and whether there is diabetic ketoacidosis or hyperosmolar hyperglycemic state.


In the hospital, blood sugar is usually lowered gradually with IV fluids, insulin, electrolyte monitoring, and treatment of the cause. Some people improve within many hours, while others need one or more days, especially if dehydration, infection, kidney problems, DKA, or HHS are present.


Helpful page: dangerous blood sugar levels.


Is Hospitalization Necessary?


With a reading of 800 mg/dL, emergency care is strongly recommended. Many patients need hospital treatment because severe hyperglycemia can cause dangerous dehydration and electrolyte problems.


If symptoms are present, call emergency services or go to the emergency department. Do not drive yourself if you feel weak, confused, dizzy, very sleepy, or unwell.


Repeat the Reading, But Do Not Delay Care


Wash and dry your hands, use a new test strip, and repeat the glucose check if you are able. Meter error, contaminated fingers, expired strips, or poor technique can sometimes cause a wrong reading.


But if the repeat reading is still very high, or if the meter says “HI,” treat it as urgent. Do not wait for it to come down by itself.


Why 800 mg/dL Is Dangerous


At this level, the main concerns are:



  • Severe dehydration

  • Diabetic ketoacidosis, especially in type 1 diabetes or insulin deficiency

  • Hyperosmolar hyperglycemic state, more common in type 2 diabetes

  • Potassium and sodium abnormalities

  • Kidney stress or kidney injury

  • Confusion, coma, or life-threatening complications if untreated


Helpful page: blood sugar level over 400 mg/dL.


Do Not Exercise to Lower It


Exercise is not safe when blood sugar is extremely high, especially if ketones are present or the person is dehydrated. Exercise may make the situation worse.


Water alone is not enough treatment for 800 mg/dL. IV fluids and monitored insulin may be needed.


Go to Emergency Care Now If You Have Any of These



  • Vomiting or inability to keep fluids down

  • Extreme thirst or very dry mouth

  • Deep or rapid breathing

  • Fruity-smelling breath

  • Confusion, drowsiness, fainting, or severe weakness

  • Abdominal pain

  • Moderate or high ketones

  • Chest pain, trouble breathing, or signs of stroke


What Doctors Usually Check


In the emergency department, the medical team may check blood glucose, ketones, blood gases or acid level, electrolytes, kidney function, urine, infection markers, heart status, and possible triggers such as infection, missed insulin, steroid medicine, heart attack, stroke, or dehydration.


Helpful resource: is my blood sugar too high or too low?



Important Safety Note


A blood sugar of 800 mg/dL should be treated as an emergency. Call emergency services or go to the emergency department, especially if you feel sick, weak, confused, dehydrated, short of breath, have vomiting, or have ketones.




Doctor’s Note


The goal is not to drop glucose as fast as possible at home. The goal is to lower it safely while correcting dehydration, electrolytes, ketones, and the cause of the crisis. At 800 mg/dL, this should be done under medical supervision.




Educational safety note: This answer is for general diabetes education only and does not replace emergency medical care. Do not delay urgent treatment for a blood sugar reading of 800 mg/dL.



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Last reviewed: July 2026.


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