What are butterfly and lance on test strip for testing glucose in blood?






Question


What are the butterfly and lance on a test strip for testing glucose in blood?





Quick Answer


The correct term is usually lancet, not “lance.” A lancet is the tiny sterile needle used in a lancing device to obtain a drop of blood. It is separate from the glucose test strip.


A butterfly mark does not have one universal meaning. On some Abbott FreeStyle products, the butterfly is part of the brand design. On certain FreeStyle readers, a butterfly icon appears on the screen while the meter processes the sample. Always follow the instructions for the exact meter and strip model rather than using the butterfly alone to decide where to insert the strip or place blood.




Answer by Dr. Albana Greca, MD, MMedSc



Hello,


A finger-stick blood glucose system normally includes a glucose meter, compatible disposable test strips, a reusable lancing device, and single-use lancets. The parts have different jobs.



Lancet, Lancing Device, and Test Strip



  • Lancet: the small sharp needle that punctures the skin.

  • Lancing device: the spring-loaded holder that contains the lancet and controls puncture depth.

  • Test strip: the disposable strip that receives the blood sample and reacts with glucose.

  • Meter: the electronic device that reads the strip and displays the glucose result.


These supplies are explained in more detail in our guide to diabetes testing strips, lancets, and lancing devices.



What Does the Butterfly Mean?


The answer depends on the device:



  • On FreeStyle Lite products, the small butterfly is mainly a recognizable Abbott FreeStyle brand mark.

  • On some FreeStyle Libre readers with a built-in blood glucose meter, a butterfly appears on the screen while the reader is processing the blood sample. The manufacturer’s instructions say not to remove the strip while that symbol is displayed.

  • Other meters may use completely different symbols, arrows, colored areas, or contact lines.


Therefore, it is unsafe to say that every butterfly marks the insertion end or blood-application area. The strip package insert or meter manual is the correct source for that model.



Which End Goes Into the Meter?


Insert only the end identified in the manufacturer’s instructions. It often has electrical contact bars, black lines, an arrow, or a shaped edge. The opposite end usually contains the sample area where blood is drawn into the strip.


Test strips that look similar are not necessarily interchangeable. Use only the strip listed for your meter. The FDA warns that an incompatible strip may produce no result or an inaccurate result.



How to Perform a Finger-Stick Test



  1. Wash your hands with soap and warm water, then dry them completely.

  2. Check that the strip matches the meter and has not expired or been damaged.

  3. Insert the strip exactly as shown in the device manual.

  4. Place a new lancet in the lancing device and select an appropriate depth.

  5. Prick the side of a fingertip rather than the center of the pad when possible.

  6. Wait until the meter signals that it is ready, then touch the correct sample area to the blood drop.

  7. Keep the strip in place until the meter confirms that enough blood was received and displays the result.

  8. Discard the used lancet in an approved sharps container and discard the strip.


Our home blood sugar testing guide explains the full process and common technique errors.




Tips for a More Accurate Result



  • Food or sugar on the fingers can falsely raise the reading, so clean and dry hands matter.

  • Do not use expired, wet, heat-damaged, or previously owned strips.

  • Do not apply blood before the meter says it is ready.

  • Use the amount of blood specified by the manufacturer.

  • Do not squeeze the fingertip excessively.

  • Store strips in their original container and close the cap promptly when required.




Can Lancets or Lancing Devices Be Shared?


No. Lancets are single-use items and should never be shared. A reusable lancing device is also for one person only, even when the lancet is changed, because microscopic blood contamination can transmit infection.



What If the Symbol or Result Is Unclear?


Do not guess. Check the model name printed on the meter and strips, read the instructions, or call the manufacturer’s support number. A pharmacist, nurse, or diabetes educator can also watch you perform a test.


If a reading is unexpected and does not match how you feel, wash and dry your hands and repeat the test with a new strip. A control-solution test can help check whether the meter and strips are working properly. Seek urgent medical help for severe symptoms or a dangerously high or low repeat result.



What I want you to remember: the lancet obtains the blood; the strip receives and analyzes it with the meter. A butterfly may be branding or an on-screen processing symbol, so always follow the manual for the exact device.




Written by: Dr. Albana Greca, MD, MMedSc, Family Physician

Medically reviewed by: Dr. Ruden Cakoni, MD, Endocrinologist

Last medically reviewed: August 4, 2026


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Safety note: Meter symbols and strip directions vary by model. Use only the compatible strip and follow the manufacturer’s instructions.



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