Blood sugar control before surgery

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Hypoglycemia or low blood sugar is when your blood sugar level is below 4.0 mmol/L. Hypoglycemia is preventable and treatable. 

Note: If you are having surgery, your blood glucose should be checked at least every 4 hours or more often if required on the morning of surgery. If you are fasting before surgery, you should also carry a fast-acting glucose source carbohydrate at all times, and when you are travelling to the hospital.

Causes of low blood sugar

Low blood sugar can occur if you:

• Do not eat enough food.
• Eat your meals or snacks too late
• Take too much insulin or diabetes pills
• Increase your activity without enough food
• Drink too much alcohol or have alcohol without food

Signs and symptoms of low blood sugar

Signs and symptoms of low blood sugar can vary between different people. When your blood sugar is too low, you may feel:

• anxious
• hungry 
• nausea
• shaky
• sweaty
• a faster heart beat
• blurred vision
• tingly or numb
• confused
• difficulty concentrating
• difficulty speaking
• drowsy
• unconscious
• unsteady/dizzy
• weak

​What to do​ if you have low blood sugar

If you have any of the symptoms and cannot test OR if you tested and your blood sugar level i​s a certain level, please follow the instructions below.

1. Below 4.0 mmol/L, take 15 grams of fast-acting glucose source carbohydrate immediately -  175mL (3/4 cup) clear apple or cranberry juice, 15 grams (3 to 5 tablets) of glucose or dextrose, or 15mL (3 teaspoons) or 3 packets of sugar. 
   
   Below 2.8 mmol/L, take 20 grams of fast-acting glucose source carbohydrate immediately - 250mL (1 cup) clear apple or cranberry juice, 20 grams (4 to 7 tablets of glucose or dextrose, check the label), 20mL (4 teaspoons) or 4 packets of sugar.
2. Wait 15 minutes. If your blood sugar remains below 4.0 mmol/L, take another 15 grams of fast-acting glucose source carbohydrate. Repeat again if necessary.
3. You should take fast-acting glucose source carbohydrate whenever there is a confirmed or suspected low blood sugar, even in the hour prior to hospital check-in time.

Special note:

If a person is unable to swallow safely or is unconscious due to a severe low blood sugar, a glucagon injection kit should be used and 9-1-1 called. You need to be prepared beforehand and teach family, friends or colleagues how to use glucagon. Talk to your health-care provider about this.

Driving and low blood sugar

Do not drive if your blood sugar level is below 5.0 mmol/L.

Low blood sugar makes you an unsafe driver.

1. Check your blood sugar before driving.
2. Check your blood sugar every 4 hours or more often on long drives.
3. Treat your low blood sugar immediately. You must wait at least 45–60 minutes after treatment before you can drive safely.
4. Your blood glucose MUST be above 5.0 mmol/L before you go back to driving.

Be prepared

• If you are fasting before surgery, you should carry a fast-acting glucose source carbohydrate at all times, also when you are travelling to the hospital.
• Have your blood glucose meter handy.
• Wear Diabetes Identification, i.e. a card, bracelet or necklace.
• Contact your doctor if you have frequent low blood sugars or if you had a severe low blood sugar.

To get ready for your upcoming surgery, a blood test called “HbA1c” will be done to check for high blood sugar (diabetes). This is a routine pre-surgical blood test. People with poorly controlled blood sugars are more likely to have complications related to inflammation and poor wound healing. You may be contacted by the pre-assessment clinic if the blood test shows your blood sugar is above normal and may be poorly controlled.

If you know you are a diabetic already, please follow up with the doctor treating your diabetes (endocrinologist, family or clinic doctor) as soon as possible. You may also be seen by a specialist from your pre-surgical team.

If a high HbA1c is new to you, you may be pre-diabetic and you should contact your family or clinic doctor to talk about the results.

What you can do to improve your health before your upcoming surgery

• Meet with your family or clinic doctor before your surgery to create a plan to treat your high blood sugar
• Avoid sweets, snacks, sweet juices or sugared soft drinks until consulting with a specialist, family or clinic doctor about your results
• Have a healthcare provider review your current medications
• Ask your family or clinic doctor regarding a diabetes clinic and if one is available in your area

More information

• Diabetes Canada 
• Diabetes Canada – Karen’s story 
• Visit www.HealthlinkBC.ca or call *811 for more information about diabetes