Article Detail

Warning signs and symptoms of high and low blood sugar

Warning signs and symptoms of high and low blood sugar

If you have diabetes or is caring for someone who has diabetes, it is important to recognize the signs and symptoms of low and high blood glucose levels and how to manage such symptoms. 

Hypoglycemia (low blood glucose)

Blood sugar level: Below 4 mmol/L. Severe hypoglycemia or blood glucose ranging between 2.0mmol/L to 3.0mmol/L, is dangerous if not treated immediately. Whilst rare, severe hypoglycemia can potentially lead to coma and death. 

Signs and symptoms:

  • Feeling hungry
  • Feeling dizzy
  • Having a headache
  • Complain of hand tremors
  • Break out in cold sweat
  • Fast heartbeat
  • Blurring of vision
  • Agitated 
  • Feeling moody and frustrated
  • Loss of concentration or unable to concentrate

What to do: 

1) Check blood glucose level. 

2) Use the 15/15 rule: Consume 15 grams of carbohydrate (half a cup of fruit juice or sugary drink, 1 tablespoon of honey or a hard candy). Check the blood glucose level in 15 minutes. Repeat the above measures if the the glucose level is still below 4.0 mmol/l. 

3) Seek immediate medical attention if the symptoms persist or they lose consciousness

After treatment and the blood glucose level has returned back to the normal range, you can let the elderly have some biscuits. It is encouraged to have some hard candy on standby in case of hypoglycemia. 

Possible reasons:

  • overdose of insulin to correct hyperglycemia
  • overdose of oral diabetic medications
  • delay of meal time after insulin administration or oral diabetic medication

How to prevent it: 

  • Don’t skip or delay meals
  • Take the medication on time, and as prescribed by the doctor
  • Monitor blood glucose before and after a physical activity
  • Record when you have hypoglycemia, so that you can identify causes and find ways to prevent them 

Hyperglycemia (high blood glucose)

Blood sugar level: 

  • fasting blood sugar or the blood sugar level after the absence of food and beverage except water overnight,  is above 7 mmol/L
  • casual blood glucose or the blood sugar level any time of the day since the last meal was consumed, is more than 11.1 mmol/L

Signs and symptoms:

  • Increased hunger
  • Extreme thirst 
  • Craving for sweet drinks to quench thirst
  • Frequent urination 
  • Sudden weight loss
  • Blurring of vision
  • Unknown reason of feeling tired
  • Restlessness and trouble concentrating  
  • Speaking incoherently and hallucinations
  • Poor wound healing or delay in healing process

What to do:

1) Check blood glucose level 

2) Check urine for ketones if blood glucose is over 240 mg/dl (> 13 mmol/l)

3) Continue to drink plenty of water

4) Seek medical attention if symptoms persist

How to prevent it: 

If you have diabetes and find it difficult to bring your blood glucose levels down to the recommended range, discuss with your doctor on how to better treat and manage your blood sugar levels. Your doctor may suggest the following treatments:

  • Getting regular exercise 
  • Adjusting the dosage of your medication or insulin to control hyperglycemia 
  • Following a diabetes eating plan with lower calorie intake 
  • Monitoring your blood sugar more frequently 

If you are have not been diagnosed with diabetes and are concerned about your high blood sugar level, you can take a diabetes risk assessment at or get yourself screened to detect diabetes early and get timely treatment. 

Do you or your elderly family member need help with blood glucose monitoring, administering insulin injections or managing diabetes? Download the Carer app and use it to hire an experienced nurse or care aide, or call us to find out more. You can also read more tips on the Carer app.  

If you have specific topics you would like us to write about, please email us at 

This article is contributed by our freelance nurse who is an expert in diabetes care.