Freestyle Libre

Web Resource Last Updated: 31-05-2023

What is Flash Glucose Monitoring?

Flash Glucose Monitoring (FGM) enables you to test your glucose levels without routinely pricking your finger. Instead, a small sensor sits on your upper arm. You scan the sensor using a handset or mobile phone. As long as the sensor is scanned adequately, it automatically measures and continuously stores glucose readings day and night.


The difference between blood glucose and sensor glucose

Unlike current blood glucose metres, the FreeStyle Libre sensor measures the glucose in the body's interstitial fluid (ISF).

Diagram showing the sensor sitting on top of the skin; layer underneath comprising of interstitial fluid and cells with glucose molecules entering from the capillary. The sensor filament is less than 0.4 mm thick and is inserted 5 mm under the skin surface

Finger prick blood glucose readings and sensor glucose readings won't always match and in fact, are likely to be different. That's because sensor glucose readings come from the interstitial fluid (ISF), a thin layer of fluid that surrounds the cells of the tissues below your skin, not from your blood. There is a 5 to 10-minute delay in ISF glucose response to changes in blood glucose, but generally, glucose readings in ISF have been proven to reliably reflect blood glucose levels.

FreeStyle Libre key points

  • A sensor lasts 14 days
  • The sensor is water-resistant in up to 1 metre (3 feet) of water for a max of 30 minutes
  • Libre should not be used above 10,000 feet
  • The handset can capture data from the sensor when it is within 1 cm to 4 cm of the sensor
  • For a complete picture of blood glucose levels, the sensor should be scanned at least once every 8 hours. Most people will want to scan more often anyway- at least 8 times a day is recommended.

Who is eligible for a Freestyle Libre?

The main points of the NHS England criteria for people that qualify for a Freestyle Libre are as follows:

  • NICE Guidelines (Updated March 2022)

    Type 1 diabetes

    • All adults with Type 1 diabetes should be offered real-time continuous glucose monitoring (rtCGM) or intermittently scanned continuous glucose monitoring (isCGM, commonly referred to as 'flash')

    • All children with Type 1 diabetes should be offered real-time continuous glucose monitoring (rtCGM). If unable to use rtCGM or a clear preference is expressed for isCGM, they should be offered intermittently scanned continuous glucose monitoring (commonly referred to as 'flash').

    Type 2 diabetes

    • Intermittently scanned continuous glucose monitoring (isCGM, commonly referred to as 'flash') can be offered to adults with type 2 diabetes on multiple daily insulin injections if any of the following apply:

      • recurrent hypoglycaemia or severe hypoglycaemia
      • impaired hypoglycaemia awareness
      • a condition or disability (including a learning disability or cognitive impairment) that means they cannot self-monitor their blood glucose by capillary blood glucose monitoring (finger prick testing) but could use an isCGM device (or have it scanned for them)
      • would otherwise need help from a care worker or healthcare professional to monitor their blood glucose
      • self-monitoring blood glucose at least 8 times a day.

    During Pregnancy

    • Type 1 Diabetes and pregnant – real-time continuous glucose monitoring (rtCGM) should be offered. Intermittently scanned continuous glucose monitoring (isCGM, commonly referred to as 'flash') should be offered if unable to use rtCGM or a clear preference is expressed for isCGM.
    • Type 2 Diabetes on insulin and pregnant - real-time continuous glucose monitoring (rtCGM) will be considered if:

      • problematic severe hypoglycaemia (with or without impaired awareness of hypoglycaemia)
      • unstable blood glucose levels despite efforts to control glucose levels

Adults with other types of diabetes

    • There is very limited NICE guidance on access to continuous glucose monitoring for people with other types of diabetes such as LADA or those caused by another illness or rare genetic condition. Check with your healthcare team. Depending on how you manage your diabetes you may or may not qualify. Your healthcare team are likely to apply the guidance for type 1 or type 2 diabetes based on the type of treatment you’re receiving for your blood glucose levels.

What does the FreeStyle Libre tell you?

  • Current glucose reading
  • Trend arrows showing if glucose levels are going up or down
  • Latest 8 hours of continuous glucose data
  • Range of reports to allowing you to look at your data and help make decisions about how you manage your diabetes
  • You can set reminders, alerts and add notes

How often do you need to scan?

  • Minimum 8 per day, including pre-meal, 2 hours post-meal, pre-bed, exercise
  • If you think you are having a hypo or are at risk of a hypo
  • Scanning after eating certain foods gives you a better understanding of how they affect your blood glucose levels
  • Frequent scanning has been shown to improve HbA1c levels

Starting out with the FreeStyle Libre

  • Prior to starting on the FreeStyle Libre, it is helpful to complete the Libre Academy.
  • Download LibreView/LibreLink app on your phone.
    • If you wish, you can share your data with your health professionals by entering your clinic ID (step by step instructions for doing this are below).
  • When adding Libre settings into your reader and phone app, set your blood glucose targets to 3.9 - 10 mmol/L to allow for post-meal readings.
  • Only give insulin to control and correct your blood glucose levels at mealtimes unless ketones are present.
  • Don't be too reactive, remember you will be scanning post-meals too.
  • Take your time and use the data to look for patterns.

The Freestyle Libre 2

What's different about Libre 2?

The main difference is that Libre 2 allows you to set alarms warning you about low and high blood glucose readings.

When will Libre 2 be available?

Libre 2 is currently being rolled out across the UK. Your prescription should automatically change when your GP system is updated, although the timing of this will vary across the UK.

If I already have Libre 1, do I need to change anything?

  • Application: There will be no changes to how you apply the sensor
  • Scanning: This depends on how you scan your Libre sensor:
    • Phone: The software/app has already been updated to be compatible with Libre 2
    • Reader: The Libre 1 reader will scan a Libre 2 sensor, but you will need to obtain a new reader if you wish to use the low/high blood glucose alarms. Libre 2 readers can be obtained through their website. Libre 1 readers are black and Libre 2 readers are dark blue.

How do I set a low or high blood glucose alarm?

Further details can be found on the Freestyle Libre website but the instructions for both phone and readers are as follows:

  • Open LibreLink
  • Go to menu
  • Tap “Alarms”
  • Touch “Low Glucose Alarm” or “High Glucose Alarm”
  • Scroll to select “Low Glucose Value” or “High Glucose Value”
  • Tap “Alarm Tone” and choose a tone
  • Touch the settings gear icon in the top right corner of the screen
  • Touch “alarms”
  • Touch “change alarm settings”
  • Select which alarm you would like to set
  • Touch “low glucose alarm” or “high glucose alarm”
  • Touch the slider to switch the alarm on
  • Use the “+” or “-“ buttons to select the glucose alarm level
  • Touch “done” to save settings

Which alarm should I set first?

Setting a low blood glucose alarm first is a good way to get used to using the alarms. Once you are comfortable with this, you could then add a high blood glucose alarm later.

What level should I set the low glucose alarm?

4.5 mmol/L, rather than the default 3.9mmol/L, is a sensible place to start so that you have a warning before you become hypoglycaemic. This choice will vary from person to person and your diabetes team can advise you on what threshold to set your low glucose alarm.

What should I do when I hear the low glucose alarm?

Scan the sensor – the low blood glucose alarm will not tell you what your blood glucose level is. You may also wish to do a finger prick check.

What about the high glucose alarm?

Once you are used to using the low blood glucose alarm, you may wish to discuss setting the high blood glucose alarm with your diabetes team.

The level at which to set the high glucose alarm will vary greatly from person to person and depends on things like your usual level of glucose and what you want to achieve with your diabetes control.

Wearing your FreeStyle Libre sensor

Skin preparation

Select an area of skin on the back of your upper arm that generally stays flat during normal daily activities (no bending or folding). Choose a site that is at least 2.5cm (1 inch) away from an insulin injection site. To prevent discomfort or skin irritation, you should select a different site to the one most recently used.

Table with two columns; situation and solution. First row; for oily surfaces; situation is soap, lotion, shampoo or conditioner might leave oily residue on your skin that may prevent the sensor from sticking problem; solution is to improve adhesion, clean your skin with soap and water, dry the skin, clean your skin with an alcohol wipe and allow the skin to air dry (do not blow on it) before proceeding; second row for wet surface; situation is moisture gets in the way of adhesion. Keep your skin dry prior to application. Solution To improve adhesion, dry the skin, clean your skin with an alcohol wipe and allow skin to air dry (do not blow on it) before proceeding; last row is hairy surface; situation is hair gets in between the skin and sensor adhesive, the solution is to clean shave the site when your sensor is to be placed

Sensor adhesion

You might find it helpful to use the following products to support adhesion. Everyone's skin is different so you may need to find the one that is right for you.

Table with 2 columns, product and description. First row; Torbot Skin Tac™, A hypo-allergenic and latex-free “tacky” skin barrier; second row;  SKIN-PREP™ Protective Barrier Wipe, Protective liquid dressing that allows skin to breathe so tapes and films adhere better; third row; Mastisol® Liquid Adhesive, Clear, non-irritating, non-water-soluble liquid adhesive that secures dressings even in moist areas

Sensor removal

If there is any residue adhesive left on your skin after removing the sensor then the following products have been found to help.

Table with two columns, product and description. First row, Baby oil, Soft moisturiser; second row, Remove™ Adhesive Remover,  Removes adhesive residue on skin; third row, UNI-SOLVE™ Adhesive Remover, Formulated to reduce adhesive trauma to the skin by thoroughly dissolving dressing tape and appliance adhesives.

Sensor wearing tips

The Freestyle Libre sensor is designed to work for up to 14 days. Some useful tips for wearing your sensor are:

  • Be careful about bumping into objects: Avoid bumping or catching your sensor on door frames, car doors, furniture, people, pets or other hard objects.
  • Touching the sensor adhesive: Avoid touching, pushing or pulling on the sensor. Also, you should avoid touching, scratching or pulling on the adhesive around the sensor, even if the adhesive has begun to peel.
  • Getting dressed: Use extra care to avoid hitting or catching the sensor on clothing while getting dressed. Avoid wearing tight clothing on your arms as doing so may pull off the sensor. 
  • Showering/bathing: The sensor is water-resistant but use extra care when cleaning around the sensor and when towelling off so that you do not catch or pull off the sensor. Do NOT take your sensor into water deeper than 1 metre (3 feet) or keep it immersed for longer than 30 minutes.
  • Contact sports: Avoid contact sports and heavy exercise with an activity that may knock off your sensor.

FreeStyle Libre apps

  1. Freestyle LibreLink app: allows you to use your smartphone to scan your sensor. You can view your current reading, trend arrow, and history. You can also look at your data for up to the last 90 days and the app provides tools to look for patterns in your blood sugars.

The FreeStyle LibreLink app is compatible with NFC-enabled smartphones running Android OS 5.0 or higher and with iPhone 7 and higher, running OS 13.2 and higher.

To use the FreeStyle LibreLink requires registration with LibreView. If you are attending a Libre education session then you may want to download the app prior to attending your session.

  1. Freestyle LibreLinkUp: allows you to share glucose readings with family, friends and healthcare professionals This means they can:
  • Remotely monitor your glucose readings and trends
  • Receive updates when your glucose readings are too high or low
  • Stay connected to help you manage your diabetes
  1. Freestyle Libreview: allows you to look at your data in detail and analysis of blood glucose patterns on a PC, laptop etc as well as share this information and analysis with your diabetes team. Each time you apply a new sensor, you need to scan with your handset before scanning with your phone if you wish to use the handset to upload your data.

How to link your Libre account to your diabetes clinic

  1. Log in to using your login and password (same as for the LibreLink phone app). Click at the top right corner to open up the menu.

2. Click 'Account Settings'.


  1. Click the 'My Practices' tab at the top of the page. Your diabetes team will provide you with a clinic ID. Type the in the box and click add - you will receive confirmation that you have added our clinic as your practice. You are able to remove this link at any time.

Looking at the information

What is happening now? Understanding trend arrows

  • If the trend arrow is straight up or down, check your blood glucose levels.
  • At mealtimes, you should calculate your normal mealtime dose (based on carb intake planned and current glucose levels), then use the arrows to make an adjustment to the dose you were planning:

10% of meal time insulin = meal time insulin ÷ 10;  20% of meal time insulin = meal time insulin ÷ 5

To understand what the trend arrows mean and what action you should take, have a look at the table below:

Table with 4 columns, arrow trend before meal-time bolus, description, how much is the glucose changing, action needed. First row, arrow pointing up, Glucose is rising quickly, this means 1 – 1.5 mmol/L in    10 – 15 minutes, Add 20% of mealtime dose as extra. Second row, arrow pointing north east, glucose is rising, this means 0.6 – 0.9 mmol/L in 10 – 15 minutes, Add 10% of mealtime dose as extra. Third row, arrow pointing east, glucose is changing slowly, this means 0.6 – 0.9 mmol/L in 10 – 15 minutes, Give usual mealtime dose. Fourth row, arrow pointing south east, glucose is falling, this means 0.6 – 0.9 mmol/L in 10 – 15 minutes, Take 10% off mealtime dose. Fifth row, arrow pointing down, glucose is falling quickly, this means 1 – 1.5 mmol/L in    10 – 15 minutes, Take 20% off mealtime dose.


Driving and FreeStyle Libre/CGM

In February 2019 the DVLA updated their guidance and approved Flash and continuous glucose monitoring devices as a legitimate way for insulin-dependent drivers to monitor glucose readings.

This guidance applies to car and motorcycle drivers who treat their diabetes with insulin. The guidance was not changed for bus and lorry drivers and they will still need to do finger-prick blood glucose readings as before.

Drivers that are using Flash and CGM devices must still confirm their blood glucose level with a finger prick test if:

  • Their glucose level is 4 mmol/L or below
  • They experience symptoms of hypoglycaemia
  • The glucose monitoring system gives a reading that is not consistent with the symptoms they are experiencing (for example, they feel the symptoms of hypoglycaemia but the reading does not indicate this)

To read further about this updated guidance regarding driving with Flash and continuous glucose monitoring devices click here.

Libre and air travel

  • The FreeStyle Libre can be passed through airport metal detectors so you are okay to keep your sensor on while going through these.
  • It should not be exposed to full-body scanners (i.e. x-ray or millimetre radio-wave).
  • To avoid removing your FreeStyle Libre sensor, you should request another type of screening to be performed by the security officer.
  • If in doubt about the type of security scan you are passing through, notify the security officer prior to proceeding through the airport security checkpoint.
  • Remember to bring medical evidence such as a letter from a medical practitioner, to confirm your medical device. Have this ready to show the security officer.

Medical device awareness card

Following a number of complaints regarding security officers asking people with devices such as CGM's or insulin pumps to either remove their device or go through body scanners, you can now carry a Medical Device Awareness Card.

The card contains information for both the passenger and security officer. It has been in use in the UK since 2019 and is endorsed by the ICAO Aviation Security Panel to improve global guidance on security screening for passengers with medical devices.

The video below gives more guidance on the Medical Device Awareness Card:

Any problems?

If you are having technical problems with your Libre (sensors falling off early/inaccurate sensors etc.) please contact Abbott customer care: 0800 170 1177 as your GP or diabetes care team cannot help with these matters.

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