The reader has a single hardware button on the front face. To swipe the sensor you must first press this button so that the “Check Glucose” screen is shown. The reader screen is touch sensitive and so most of your interaction with the reader will be by touching the screen. The hardware button is a general “back” or “cancel” button. So if you want to read data on the reader without scanning, you press the hardware button once to get the “Check Glucose” screen then cancel this screen by pressing the hardware button again to get to the main screen and through the main screen access the data through the “Review History” button . Similarly, to switch off the screen you press the hardware button one or more times until you get to the main screen then press the hardware button again to get to the “Turning reader off” screen and either wait for the screen to turn off, or press the hardware button to switch it off immediately.
Some of the menus will have more items than can be shown on the screen and so there will be up and/or down arrows to access these other items. In some cases you will get a full screen dialog box, which is indicated by an OK button in the top right hand corner. If this is a dialog which you can enter data (and it won’t always be) then touching OK will save the settings you change. Otherwise you can press the hardware button to cancel the data changes and close the dialog.
However, inconsistently, some dialogs have a blue [done] button in the bottom right hand corner to allow you to save changes, but again, you can cancel changes by pressing the hardware button. Finally, there are some screens which just display data and these will have an OK button in the top right hand corner to allow you to close the screen. For such windows it is irrelevant whether you touch the OK button or press the hardware button, they will have the same effect.
It is important that you remember that whenever you change a value you should use the onscreen buttons (OK or [done]) to save the data and only use the hardware button to cancel changes.
Finally, it is worth pointing out that if you press and hold the hardware button for more than 30 seconds this will “restart” the reader but the data and settings on the reader will be retained. Experience shows that after using the reader for a couple of months it starts to slow down, and this can be remedied by a restart.
Scanning Data
To download data from the sensor to the reader you “swipe” the sensor. This means that you place the reader (or phone) close to the sensor. It does not have to come into physical contact, and you can swipe the sensor through several layers of clothes.
The data that is downloaded is the last fifteen minutes of one minute readings and the last eight hours of the fifteen minute averages. The reader then displays a graph showing the last eight hours of fifteen minute readings against a time scale, it also shows the most recent reading and it shows a trend arrow. The trend arrow is one of six arrows with the trend calculated from the last fifteen one minute readings. The trend arrow gives you an indication about how your glucose is currently changing, but you can also view the 8 hour graph to get an idea of how your glucose is changing.
The direction of the arrows give an indication of how quickly your glucose is changing. An up arrow (↑) or a down arrow (↓) indicates that your glucose is increasing or decreasing at greater than 0.1 mmol/l per minute. So in ten minutes or less, your glucose could change by 1 mmol/l.
A level arrow (→) indicates that your glucose is roughly stable and that any changes are less than 0.06 mmol/l per minute. It is important to realise that the level arrow could mean that your glucose could change by 1 mmol/l in 20 minutes, so do not assume that it means “stable”.
A diagonal up arrow or a diagonal down arrow shows that your glucose is changing between 0.06 and 0.1 mmol/l per minute. This means that your glucose could change by 1 mmol/l in 10 to 17 minutes.
The final “arrow” isn’t one. If the figure is shown without an arrow it means that no obvious trend can deduced and so it is prudent to swipe in a few minutes time to see if a trend can be calculated. In this situation the trend graph is important because you can see from the direction of the graph how your glucose is changing. Typically you’ll see a value without an arrow when your glucose has ‘peaked’ after eating and is about to go down.
What does this mean in practice? Well, the arrows will allow you to see how an intervention is affecting you. So if you are hypo and you eat some glucose, you hope to see a ↑ to show that the hypo has been treated. However, you will also want the rise to keep you within your personal glucose target, so at some point you will want the rise to stop. That means you expect to see the ↑ change to a diagonal up arrow and then change to a → indicating a peak.
A temptation with treating a hypo is to eat until sated, and this can mean over eating which will lead to high glucose readings. Healthcare professionals recommend 10g to 15g glucose as a treatment, and Libre enables you to determine what is right. When hypo you can take 10g and then check in 30 minutes to see that the trend arrows indicate that your glucose is rising. If not, then you can eat more glucose.
The trend graph also gives a wealth of information. Ideally, your glucose should be level within the target range that you have determined. The graph will show spikes from immediate interventions: when you have eaten carbs or taken insulin to treat a high. It will also show broad peaks, of slowly rising glucose from not enough insulin or slowly falling glucose from slightly too much. While you may decide to intervene in response to these broad peaks, they also give you information for later actions. A broad high or low may indicate that your basal needs adjusting, or that your carbs to insulin ratios need changing.
Scan Notes
When you scan the sensor the scan screen will show a blue button with pencil in the top right hand corner, touching this will show the “Add Notes” screen. This has a series of check boxes, some will add a text note, and others allow you to add a data value.
The standard text notes are Exercise and Medication, but you can add you own values with the desktop app. In addition there are three standard items: Rapid Acting Insulin, Long Acting Insulin and Food. With these items, when you check the appropriate box a blue button with a [+] will be show. If you save the data at this point (touch the OK button) then a text value will be saved indicating that you had insulin or carbs but did not give a value. To add a value you must touch the [+] button and this will send you to another screen that allows you to add the amount of insulin (in insulin units) and the amount of carbs (in grammes). You are limited to 50u for either rapid or basal insulin and a whopping 200g for carbs. If your insulin dose is greater than 50u then you will have no option other than to scan again and add the excess over 50u.
The carbs screen behaves slightly differently to the insulin screens because when you first touch the up arrow to increase the value it will initially start at 15g, so if you want to add less than that you will need to use the down button to decrease it. In addition, the carbs screen has two check boxes to add an alarm either one hour or two hours later.
If you do not add notes through the scan results screen you can add it through the Logbook menu. However, note that you only have 15 minutes after the scan to do this, and you can only change the last reading. So if you scan to see your glucose and then inject but forget to add the bolus, you only have 15 minutes to edit the value, otherwise you’ll have to scan again and add the bolus to the new value and remember that you added an extra 15 minute delay.
To be frank, it is very irritating that you cannot edit the scan notes you have added. Many of the analysis pages in the desktop app reports rely on carbs or insulin values and gaps in the data make those reports fairly useless. It would be much better if Abbott allowed you to edit these user entered values, most likely through the desktop app.
Libre User 