High blood glucose level even after taking insulin

by Lulu





Question from Lulu:


Hello Doctor,


I have a relative that has a high blood sugar that isn't going down even after taking insulin. This has been for couple of days now and still has not seen a doctor since his doctor is on leave.


If it stays like this, then an immediate action needs to be done? What could that be? Increasing the insulin shots?


He also has been lately very pale, should we be concerned or is it just fatigue?


Any check up would you highly recommend for the time being?


It would be highly appreciated if you can provide me with your medical advise.


Thank you.





Quick Answer


Yes. Persistently high blood glucose despite insulin for several days needs urgent medical assessment today. Do not wait for the usual doctor to return, and do not increase or repeat insulin doses unless the person has a written correction plan from the diabetes team. Extra doses taken too close together can overlap and cause delayed severe hypoglycemia.


Check the glucose again after washing and drying the hands. If it remains around 300 mg/dL (16.7 mmol/L) or higher, check blood or urine ketones if available and contact an urgent-care service or diabetes clinician immediately. Go to the emergency department for moderate or high ketones, vomiting, abdominal pain, deep or difficult breathing, fruity breath, marked dehydration, confusion, unusual sleepiness, chest pain, fainting, or glucose that is not improving with the prescribed plan.




Answer by: Dr. Albana Greca Sejdini, MD, MMedSc



Why insulin may not be lowering the glucose


Lulu, this does not automatically mean the insulin has permanently “stopped working.” Common causes include:



  • Illness or infection, even before fever or obvious symptoms appear

  • A missed dose, incorrect dose, wrong insulin, or incorrect timing

  • Insulin that was frozen, overheated, expired, or stored improperly

  • Injecting repeatedly into lumps, thickened skin, scars, or sunken areas

  • A blocked, leaking, disconnected, or displaced insulin-pump infusion set

  • Steroids and some other medicines that raise glucose

  • Dehydration, pain, surgery, heart attack, or stroke

  • Carbohydrate intake that is not matched by the prescribed insulin plan


Diabetic ketoacidosis can occur when the body does not have enough effective insulin. It can occur in both type 1 and insulin-treated type 2 diabetes. Hyperosmolar hyperglycemic state is another serious emergency, particularly in type 2 diabetes.




Go to emergency care now if any of these occur



  • Blood glucose remains at or above 300 mg/dL despite the usual prescribed correction plan

  • Moderate or high ketones, or blood ketones above the limit given by the care team

  • Repeated vomiting or inability to keep fluids down

  • Abdominal pain, deep or rapid breathing, or fruity-smelling breath

  • Confusion, severe weakness, unusual drowsiness, fainting, or seizure

  • Chest pain, stroke symptoms, severe shortness of breath, or bluish/gray skin


Do not let the person drive if weak, confused, drowsy, dizzy, or visually impaired.




Should the insulin dose be increased?


Only according to an existing correction or sick-day plan. The correct dose depends on the insulin type, time of the previous dose, current glucose, ketones, food intake, kidney function, illness, and insulin still active in the body. Repeating rapid-acting insulin too soon can cause “insulin stacking” and a dangerous low several hours later.


Do not stop basal insulin in someone with type 1 diabetes merely because the person is eating less, unless an emergency clinician specifically instructs otherwise. If a pump is used, check the tubing, reservoir, cannula and site and follow the pump-failure instructions.



What to do while arranging medical help



  1. Wash and dry the hands, repeat the glucose test, and record the time and result.

  2. Check ketones if the person has been taught to do so, especially when glucose is above 250 mg/dL or illness is present.

  3. Review the insulin label, dose, injection time, storage conditions and expiration date.

  4. Use only the prescribed correction plan. Do not borrow insulin or estimate an extra dose.

  5. Sip water or sugar-free fluids if alert, able to swallow, not vomiting, and without a fluid restriction.

  6. Avoid vigorous exercise when glucose is very high or ketones are present.

  7. Contact another clinician, the diabetes service, urgent care, or the emergency department; do not wait longer.



What could the paleness mean?


Paleness is not enough to diagnose liver damage. Liver or bile-duct problems more often cause yellowing of the skin or eyes rather than simple pallor. Pale appearance may occur with anemia, dehydration, infection, low blood pressure, poor circulation, blood loss, kidney disease, or another illness. Because it is new and occurs with persistent hyperglycemia, it strengthens the need for examination.



Checks a clinician may consider










CheckWhy it may be needed
Blood glucose and blood or urine ketonesAssess severity and possible ketoacidosis.
Electrolytes, bicarbonate, kidney function and blood acidityLook for dehydration, electrolyte disturbance, DKA or hyperosmolar crisis.
Complete blood countEvaluate pallor, anemia or possible infection.
Urine testing and infection assessmentIdentify urinary or other infections that may raise glucose.
Medication, injection-site and insulin-storage reviewFind dosing, delivery, absorption or product problems.
Other tests guided by symptomsMay include ECG, chest testing, liver tests or imaging when clinically indicated.


For general safety guidance, see dangerous blood sugar levels and the guide to insulin treatment, dosing and sick-day safety. The insulin correction calculator should be used only with personal ratios and correction factors supplied by the diabetes team—not to invent an emergency dose.



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References




Medically reviewed by: Dr. Ruden Cakoni, MD, Endocrinologist

Last reviewed: July 2026


Medical disclaimer: Educational only—not personal medical advice. Diagnosis and treatment should come from a qualified clinician who knows the patient’s medical history.



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