The word “fasting” means to intentionally abstain from food. People fast for different reasons. Your doctor may ask you to fast before a medical test. Some fast as part of their religious practice. There are even weight-loss plans that involve fasting for a specific amount of time. Whatever your reason, it is essential to discuss any type of fasting with your doctor before you get started—especially if you have diabetes.
Fasting for Labs and Procedures
Your doctor may ask you to go without food and/or drink in the time leading up to a test or procedure.
At least 1-2 weeks before:
- Tell the facility that you have diabetes when scheduling your lab work or procedure. Try to schedule your test for first thing in the morning. This will limit the amount of time you have to go without food (and possibly meds).
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Ask your provider:
- Do I need to fast for these labs? (Many routine labs don’t require fasting.)
- Should I stop taking my meds? If so, when?
- Will the medication I’m on cause low blood sugar while I’m fasting?
- How often should I check my blood sugar while fasting?
- How can I treat low blood sugar while fasting?
The day of your test/lab work:
- Continue checking blood sugar frequently. This will help you prevent low blood sugar.
- Check your blood sugar before driving. If it’s not in a safe range, don’t get in the driver’s seat; consider asking a friend or family member to drive instead.
- If your blood sugar is low, follow these guidelines.
- Remind the provider that you have diabetes. If you had to treat low blood sugar before coming in, let them know.
- Tell the provider when you last ate, what you ate, and when you last took your diabetes meds.
- Bring a balanced snack to eat once your test is done. Here are some ideas.
Religious Fasting
Part of your religious observance may include a full or partial fast for a given period of time.
Before:
- Tell your doctor when you will be fasting and for how long.
- Make a plan with your doctor. Talk about how often you will check blood sugar and how you will treat low blood sugar. You will also want to address possible changes to your meds.
- Discuss risks with your doctor, especially if you have diabetes complications like heart disease, kidney disease, or poor vision.
- Keep in mind that there may be religious exceptions when it comes to fasting with a medical condition.
During:
- Pay close attention to how you are feeling. If you’re feeling off (lightheaded, dizzy, or shaky), this may signal blood sugar fluctuations.
- Feeling off or have low blood sugar symptoms? Check your blood sugar right away.
- If your blood sugar is less than 4,0mmol/L, treat with 3-4 glucose tablets or 4 ounces of juice or soda. Then, recheck in 15 minutes to be sure your levels are trending up.
Intermittent Fasting
Some people fast as a way to lose weight or control medical conditions. There are different styles of intermittent fasting. We don’t yet know the long-term impacts of intermittent fasting on humans.
Before:
- Create a blood sugar plan with your doctor that fits your eating/fasting pattern. Be sure to include:
- How long you will be fasting.
- How often you will be checking your blood sugar.
- How your meds will change.
During:
- If you have low blood sugar symptoms, check your blood sugar.
- If your blood sugar is less than 4.0mmol/L, treat promptly with a fast-acting carbohydrate source. 3-4 glucose tablets or 4 ounces of juice or soda are good options. Recheck in 15 minutes to ensure levels are trending back up to a healthy range. Afterward, have a balanced snack or meal to help maintain your blood sugar levels.
- Stay hydrated with water.
- Choose foods that are high in fiber such as non-starchy vegetables, fruits, whole grains, and legumes. This will help keep you satisfied for longer during the fasting period.