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freestyle libre vitamin c sensor issues inaccurate false readings

If you use the Freestyle Libre CGM this article is for you! Learn the connection between the Freestyle Libre CGM sensor and vitamin C.

Freestyle Libre and Vitamin C – False Readings

To get the most accurate CGM readings there are a few things you need to know about… like compression lows, proximity to your insulin injections, and more.

And if you have the Freestyle Libre CGM then you can add vitamin C to that list.

Since Libre’s inception, Vitamin C has played a critical role in its accuracy. Even tho Abbott continues to come out with new models, their sensor chemistry has not changed.

On their indications & important safety information page they state,

“Taking ascorbic acid (vitamin C) supplements while wearing the sensor may falsely raise sensor glucose reading. Taking more than 500 mg of ascorbic acid per day may affect the sensor readings which could cause you to miss a severe low glucose event.”

Abbott, Freestyle Libre
freestyle libre interfering substances vitamin c

What does 500 mg a day look like?

  • 4 glasses of orange juice
  • 11 oranges
  • 2.5 cups of red bell pepper
  • 3.5 kiwis
  • 6 cups of strawberries
  • 3.5 cups of broccoli

Unless you’re chasing lows all day with OJ, or pounding strawberry smoothies, it’s pretty hard to hit 500mg of vitamin C a day via whole foods.

What you do need to watch out for is supplements.

Supplements that contain over 500mg include:

  • Airborne® (1,000 mg)
  • Emergen-C® (1,000 mg)
  • and many other Vitamin C supplements

Can I Still Use My CGM When Taking Vitamin C Supplements?

Yes! However, I wouldn’t bolus off the CGM results since they would be inaccurate. I would stick to finger sticks for the day(s) that you’re taking heavy dose supplements of Vitamin C.

Personally, I haven’t seen that the effects last past a few hours of taking high dose vitamin C, and the readings for me were never too far off, but you should definitely try it out yourself.

Will Abbot Change Their Sensor Chemistry?

Abbot is working on eliminating this issue because it is one of the reasons the FDA did not approve them to be an iCGM authorized for automated dosing systems.

Share with a T1D you love Please share Freestyle Libre and Vitamin C – False Readings with someone who uses the Freestyle CGM! Sharing helps more people find this blog. Thank you!

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Leave A Comment

  1. Carey March 31, 2022 at 11:07 am - Reply

    Very good to know! I’ve been using freestlye for years and had no idea about this. and i’m fairly certain i’ve taken airborne during that time too hahah – Oops!

    • T1D Living April 5, 2022 at 10:57 am - Reply

      Hahaha! I’ve taken high dose vitamin C without knowing this connection too.

  2. Amanda March 31, 2022 at 12:36 pm - Reply

    this reminds me of dexcom with tylenol, same issue. Thank you for this. I’ve been using libre for over a year now and love it.

    • T1D Living April 5, 2022 at 10:57 am - Reply


  3. Rick Phillips March 31, 2022 at 9:09 pm - Reply

    wow, that is good to know. Thank you.

    • T1D Living April 5, 2022 at 10:58 am - Reply

      you’re welcome!

  4. John April 7, 2022 at 2:18 am - Reply

    I am recently diagnosed, use diet and exercise instead of medicine… I go a little overboard… I wear the Libre 14 day and test regularly with both Accu Chek and One Touch… I take 1000mg of C daily, and i have not seen it affect the Libre’s accuracy… and i compare it to meter readings often

    • T1D Living April 18, 2022 at 12:12 pm - Reply

      That’s awesome you’re seeing so much accuracy!

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