Common Mistakes to Avoid When Taking a Blood Sugar Test

17 Sep 2025 By Rachael C. Passmore, D.O.

Common Mistakes to Avoid When Taking a Blood Sugar Test

Managing diabetes effectively requires regular monitoring of blood sugar levels. Accurate readings are crucial for making informed decisions about medication, diet, and exercise. However, many individuals unintentionally make mistakes during blood glucose testing, leading to inaccurate results and potentially impacting their health. This article outlines common pitfalls to avoid when taking a blood sugar test to ensure you get the most reliable and accurate data possible.

Why Accurate Blood Sugar Testing Matters

Accurate blood glucose readings are the cornerstone of diabetes management. These readings help you:

Monitor the effectiveness of your diabetes treatment plan: See how medications, diet, and exercise are impacting your levels.
Detect hyperglycemia (high blood sugar) and hypoglycemia (low blood sugar): Identify when your levels are outside the target range and take appropriate action.
Make informed decisions about meal planning: Understand how different foods affect your blood sugar.
Adjust insulin dosages (if applicable): Determine the correct amount of insulin to administer.
Prevent long-term complications: Maintaining stable blood sugar levels reduces the risk of nerve damage, kidney problems, vision loss, and heart disease.

| Importance of Accurate Blood Sugar Testing | Details | | :----------------------------------------- | :---------------------------------------------------------------------- | | Treatment Effectiveness | Reveals how well medications, diet, and exercise are working. | | Hyperglycemia/Hypoglycemia Detection | Identifies when levels are too high or too low. | | Informed Meal Planning | Guides choices about foods to maintain stable glucose levels. | | Insulin Dosage Adjustment | Provides data to determine accurate insulin doses. | | Prevention of Long-Term Complications | Reduces risks such as nerve damage, kidney problems, vision loss, etc. |

1. Neglecting to Wash Your Hands Properly

One of the most prevalent mistakes is not washing your hands thoroughly before testing. Even seemingly clean hands can have traces of food, lotion, or other substances that can contaminate the blood sample and elevate your blood glucose reading.

The Right Way to Wash Your Hands

Use warm water: Warm water helps to increase blood flow.
Use soap: Plain soap is generally sufficient. Avoid antibacterial soaps that can leave a residue.
Scrub thoroughly: Wash for at least 20 seconds, ensuring you clean between your fingers and under your nails.
Rinse well: Rinse thoroughly to remove all traces of soap.
Dry completely: Use a clean towel or air-dry your hands before testing. Make sure your hands are completely dry, as water can also affect the accuracy of the reading.

Real-World Example

A study published in the Diabetes Care journal showed that washing hands with soap and water lowered blood glucose readings by an average of 0.3 mmol/L (5.4 mg/dL) compared to using alcohol-based hand sanitizers. This underscores the importance of proper hand hygiene to avoid falsely elevated readings.

2. Using Expired or Improperly Stored Test Strips

Blood glucose test strips have expiration dates for a reason. Expired strips may not provide accurate results because the chemicals on the strips can degrade over time. Furthermore, improper storage, such as exposing the strips to heat, moisture, or humidity, can also affect their accuracy.

How to Store Test Strips Correctly

Check the expiration date: Always check the expiration date before using a strip. Discard expired strips properly.
Store in a cool, dry place: Keep the test strip container in a location away from direct sunlight, heat, and moisture. Avoid storing them in the bathroom or near the kitchen sink.
Keep the container tightly closed: This protects the strips from humidity and contaminants.
Use strips from their original container: Never transfer strips to a different container, as this can expose them to moisture or damage.

What Happens If You Use Expired Strips?

Using expired blood glucose test strips can lead to:

Falsely low readings: Which can cause you to underestimate your blood sugar levels.
Falsely high readings: This may result in overtreatment, such as taking more insulin than necessary.
Inaccurate A1c values over time: Over time, the accumulative inaccuracies can result in you misunderstanding your actual control of your diabetes.

3. Insufficient Blood Sample

Obtaining a sufficient blood sample is vital for an accurate reading. If the sample is too small, the meter may display an error message or provide an inaccurate result. Often, people are too tentative when drawing blood, but doing so almost guarantees failure.

Tips for Obtaining an Adequate Blood Sample

Use the correct lancing device setting: Adjust the depth of the lancing device to ensure it penetrates the skin adequately, but not excessively.
Prick the side of the fingertip: The sides of the fingertips are less sensitive and have better blood flow than the center.
Alternate fingers: Repeatedly pricking the same finger can cause soreness and calluses, reducing blood flow.
Warm your hands: Warming your hands with warm water or by rubbing them together can improve blood flow.
Apply gentle pressure: After pricking your finger, gently apply pressure to encourage blood flow. Avoid squeezing too hard, as this can dilute the sample with tissue fluid.
Avoid milking the finger: “Milking” the finger or squeezing too tightly can dilute the blood sample with interstitial fluid, leading to inaccurate results.

What If You Still Can't Get Enough Blood?

If you consistently struggle to obtain an adequate blood sample, consider:

Reviewing your technique with a healthcare professional: A diabetes educator can provide personalized guidance.
Using a different lancing device: Some devices are more effective than others.
Discussing the issue with your doctor: There may be underlying factors affecting your circulation.

4. Not Coding the Meter Correctly

Some blood glucose meters require manual coding, where you need to enter a code that matches the code on the test strip vial. Failing to code the meter correctly can lead to significantly inaccurate readings. More modern meters automatically code, but you should understand your machine to confirm. How To Lower Your A1C Blood Sugar A Step By Step Plan

Why Coding Matters

Coding calibrates the meter to the specific batch of test strips you are using. Each batch can have slight variations, and coding ensures the meter accurately interprets the results.

How to Code Your Meter

Check the test strip vial: The code is usually printed on the label of the test strip vial.
Enter the code into the meter: Follow the manufacturer’s instructions for entering the code. This usually involves using the meter’s buttons to navigate to the coding menu and entering the correct number.
Verify the code: Double-check that the code displayed on the meter matches the code on the test strip vial.
Use auto-coding: Many modern meters feature auto-coding, meaning the meter automatically recognizes the code on the test strip. However, it is still important to verify that the meter has correctly identified the code.

The Consequences of Incorrect Coding

Incorrect coding can lead to:

Significant errors in blood glucose readings: The readings may be much higher or lower than your actual blood sugar level.
Incorrect insulin dosages: Leading to hyperglycemia or hypoglycemia.
Compromised diabetes management: Inaccurate data can make it difficult to manage your diabetes effectively.

5. Testing at the Wrong Time or Frequency

The timing and frequency of blood glucose testing can significantly impact the accuracy and usefulness of the data. Testing sporadically or at inappropriate times may not provide a clear picture of your blood sugar patterns. How To Lower Your Blood Sugar Naturally A Beginner S Guide

Recommended Testing Times

Fasting blood sugar: Test in the morning before eating or drinking anything (except water).
Before meals: Test before breakfast, lunch, and dinner to see your baseline level.
Two hours after meals: Test two hours after the start of a meal to see how the meal affected your blood sugar.
Before bedtime: Test before going to bed to ensure your blood sugar is in a safe range overnight.
Before, during, and after exercise: Testing during exercise can help you understand how physical activity affects your blood sugar.
When you suspect low blood sugar: Test immediately if you experience symptoms of hypoglycemia (e.g., shakiness, sweating, confusion).
When you are sick: Illness can significantly affect blood sugar levels, so more frequent testing is usually necessary.

How Often Should You Test?

The frequency of blood glucose testing depends on several factors, including:

The type of diabetes you have: Individuals with type 1 diabetes typically need to test more frequently than those with type 2 diabetes.
Your treatment plan: If you take insulin, you will likely need to test more often than if you manage your diabetes with diet and exercise alone.
Your blood sugar control: If your blood sugar levels are unstable, you may need to test more frequently to identify patterns and make adjustments to your treatment plan.
Your doctor's recommendations: Your doctor will provide personalized recommendations based on your individual needs.

Consistency is Key

Establishing a consistent blood glucose testing routine can help you:

Identify trends and patterns: Allowing you to see how your blood sugar levels respond to various factors, such as meals, exercise, and medications.
Make timely adjustments to your treatment plan: Prevent hyperglycemia and hypoglycemia.
Improve your overall diabetes management: Achieve better blood sugar control and reduce the risk of long-term complications.

6. Ignoring Meter Maintenance and Calibration

Blood glucose meters, like any other electronic device, require regular maintenance and calibration to ensure accuracy. Ignoring these essential steps can lead to unreliable readings and compromised diabetes management.

Key Maintenance Steps

Clean your meter regularly: Follow the manufacturer's instructions for cleaning your meter. Use a soft, damp cloth to wipe the exterior of the meter. Avoid getting liquid inside the meter.
Handle the meter with care: Avoid dropping or exposing the meter to extreme temperatures, humidity, or direct sunlight.
Replace the batteries as needed: Low batteries can affect the accuracy of the meter. Replace the batteries when the meter indicates they are low.

Calibration Solutions

Calibration solutions, also known as control solutions, contain a known amount of glucose. Using a control solution to test your meter helps ensure it is providing accurate results.

How to Use Control Solutions

Obtain a control solution: Purchase a control solution that is compatible with your meter.
Perform a control test: Follow the manufacturer’s instructions for performing a control test. This usually involves applying the control solution to a test strip and inserting it into the meter.
Compare the result to the expected range: The control solution vial will specify the expected range for the control test. Compare the result displayed on the meter to this range.
Troubleshoot if the result is outside the range: If the result is outside the expected range, consult the manufacturer’s instructions for troubleshooting. This may involve cleaning the meter, replacing the batteries, or repeating the control test. If the problem persists, contact the manufacturer or your healthcare provider.

How Often to Perform a Control Test

When you first get your meter: Perform a control test to ensure the meter is working correctly.
When you open a new vial of test strips: The strips in a new vial may have slightly different characteristics than those in the previous vial.
If you suspect your meter is not providing accurate results: E.g., your blood glucose readings do not match how you feel.
If you drop your meter: A fall can damage the meter’s internal components and affect its accuracy.
At least once a month: Regular control testing helps ensure your meter is consistently providing accurate results.

Seeking Professional Guidance

If you are unsure about any aspect of blood glucose testing or meter maintenance, consult your healthcare provider or a certified diabetes educator. They can provide personalized guidance and answer any questions you may have.

By avoiding these common mistakes, individuals with diabetes can ensure they are obtaining accurate blood sugar readings, which is vital for effective diabetes management and preventing long-term complications. Consistently adhering to proper testing techniques, using well-maintained equipment, and seeking professional guidance when needed can significantly improve your health outcomes. The Complete Guide To Blood Sugar Tests At Home And At The Doctor