Fasting before a blood sugar test ensures accurate results by providing a baseline unaffected by recent meals. Here's what you need to know:

• What to do: Fast for 8–12 hours before the test. Only drink water.
• What to avoid: No food, flavoured drinks, coffee, alcohol, or gum. Avoid intense exercise and smoking.
• When to schedule: Morning tests are ideal after an overnight fast.
• Hydration: Drink plenty of plain water for easier blood draws.
• Medications: Consult your doctor about any necessary adjustments.

Quick tip: If you accidentally eat or drink, inform your healthcare provider for proper interpretation. Follow these steps to ensure reliable test results.

Fasting for blood sugar tests: The basics

Here’s a simple breakdown of what fasting means, why it matters, and how it helps give the most accurate blood sugar results.

How fasting affects blood sugar

Fasting helps clear the influence of recent meals, giving a clear baseline for blood sugar levels. For healthy individuals, blood sugar should be below 5.56 mmol/L. Levels between 5.56–6.94 mmol/L may suggest prediabetes, while 7.0 mmol/L or higher could indicate diabetes.

With this in mind, it’s important to understand the fasting times required for different types of tests.

Required fasting times

Here’s a quick look at common blood sugar tests and their fasting requirements:

For tests that require fasting, the usual duration is 8 to 12 hours, during which only water is allowed.

If you have diabetes or other medical conditions, consult your doctor to confirm the correct fasting procedure.

Follow these guidelines to help ensure accurate test results.

Learn how to get the most accurate results from your glucose test with our simple preparation guide.

Steps to prepare for your test

Follow these simple steps to get your body ready and make sure your blood sugar test goes smoothly and accurately.

Picking the best test time

Plan to schedule your test in the morning after an overnight fast. This takes advantage of your body's natural fasting period.

Staying hydrated is also important for a smoother blood draw.

Drinking water during fasting

Stick to plain water to stay hydrated during your fasting period. Here's a quick guide:

Make sure to drink plenty of water in the 48 hours leading up to your test. Have several glasses right before the blood draw and continue drinking plain water during the fast.

In addition to hydration, it's crucial to check how your medications might affect the test.

Managing medications

Some medications can influence blood sugar levels, so reviewing your medication schedule is key. Here's what to do:

• Write down all medications you're taking, including prescriptions, over-the-counter drugs, vitamins, and supplements.
• Talk to your healthcare provider ahead of time to learn if any adjustments are needed.
• Follow their instructions exactly - don't make changes on your own.

Clear communication with your healthcare team ensures you’re fully prepared for accurate test results.

‍Curious how 16:8 fasting influences your metabolic health? Read our full guide to find out more.

What not to do while fasting

To get accurate blood sugar readings while fasting, it's important to avoid certain foods, drinks, and activities.

Foods and drinks to avoid

Stick to plain water during fasting and steer clear of the following:

Activities to void

Certain activities can also disrupt your blood sugar levels during fasting.

Exercise restrictions:

• High-intensity interval training (HIIT)
• Resistance or strength training
• Strenuous aerobic exercises

These types of workouts can release stress hormones, which may elevate blood sugar levels.

Additionally, avoid these habits while fasting:

• Chewing gum
• Smoking

Both can interfere with the fasting process and potentially impact your results.

Tips for better test results

Improve your test outcomes with these practical strategies.

Reducing test anxiety

Feeling anxious before a blood test is common. Here are some ways to ease your nerves:

• Schedule your blood draw between 7:00 AM and 9:00 AM for a smoother experience.

After the test, focus on recovery and keeping an eye on how your body responds.

After your test

Pay attention to how your body reacts after fasting. If you notice anything unusual, contact your healthcare provider.

If you're a Vively user with a CGM, you can use the app to track your glucose levels after the test and gain helpful recovery insights.

Wondering what the best way to break your fast is? Check out our complete guide for healthy, balanced post-fast meals.

Monitoring blood sugar with CGM

Continuous glucose monitoring (CGM) offers real-time data on your glucose levels, revealing patterns that standard tests might miss. A CGM sensor keeps track of your glucose levels continuously, giving you a full picture of how your body responds during fasting. Here's how Vively's CGM can help improve your fasting test preparation.

CGM and fasting tests

Vively's CGM system provides several benefits, including:

• Real-time glucose tracking during fasting
• Identifying patterns in your fasting response
• Detecting dawn phenomenon, which traditional tests often overlook

"The Vively app with the CGM has highlighted that I am still insulin resistant and need to focus daily on foods I consume, it also showed I suffered from dawn phenomenon which quarterly bloods would never show." - Adam

"The glucose monitor provides valuable insights, especially on how the body reacts before and after the meal. I've gained a better understanding of what I should eat and what I need to cut off." - Renee

Read more Vively member stories here.

The Vively app enhances the CGM experience by:

• Syncing with other health apps for a broader view of your health
• Logging meals and fasting periods
• Offering weekly trend analysis for better insights

These tools make it easier to prepare for your fasting blood sugar test by:

• Tracking glucose levels during the 8–12 hour fasting window
• Monitoring the timing of your last meal
• Recording factors that might affect test results

The lightweight, water-resistant sensor provides uninterrupted monitoring, even during fasting. Over 12,000 Vively members have used this technology to gain a deeper understanding of their glucose patterns.

Conclusion

Preparing for a blood sugar test requires careful planning to ensure accurate results. You’ll need to fast for 8–12 hours before your test. During this time, water is the only thing you should consume - avoid all other food and drinks.

Here are some key tips to follow:

• Schedule your test for early in the morning, and drink plenty of water to make the blood draw easier.
• Avoid chewing gum, smoking, or engaging in intense physical activity while fasting.

To maintain test accuracy:

• Talk to your healthcare provider about your medication schedule.
• Stay away from alcohol the night before your test.
• If you’re feeling very unwell, consider rescheduling.

Stress and poor sleep can also affect your blood sugar levels. If you mistakenly eat or drink anything other than water during the fasting period, let your healthcare provider know right away so they can interpret your results correctly.