Getting Started with Continuous Glucose Monitoring
By Linda Mackowiak, MS RN CDE
Continuous Glucose Monitoring (CGM) Is Here!
It has been a long wait for many of us, and our expectations are high. I would like to share some information with you that I hope will help you get started and achieve success with CGM. This information does not replace the care from your health care provider (HCP). You may find some ideas here to discuss with your HCP as you begin using this new technology.
What do you expect from CGM? What is CGM?
CGM is new and it is possible that your expectations may not end up being exactly the same as the benefit you will find. For example, you may want CGM for alarms to tell you when you are high and low. Imagine these additional possibilities:
CGM is all about these things ... and more.
- Checking your blood glucose and seeing the number 80 mg/dl. Wouldn't it be helpful to be able see 80mg/dl and rising, or 80 mg/dl and falling, or 80 and relatively stable?
- Finding glucose trends before they become problems.
- Looking back and seeing what just happened so you can learn more about your diabetes self-care.
- Looking back over a longer period of time, to learn about patterns and why some days are different.
Diabetes is so hard
If you are reading this, then you know what I mean. You are already working very hard at your diabetes self- care and doing the best you can. Sometimes we wish and need help with this disease, and we may look to a new technology to do more than it can do. CGM is not a cure, but it has so much to offer the person with diabetes.
You will still have to check your blood glucose, have your brain make decisions that other people's pancreas would make , and you will still need to keep a check on safe glucose levels. CGM may warn you about many or most, but not always every low glucose you have. However, it may give you so much more information about how your low glucose levels happen, what you can do to prevent them, and how to treat them without overtreating and causing exactly what you don't want - a big rise in your glucose level.
CGM will not result in your having perfect glucose readings all the time. For example, balancing insulin and food is such a difficult task for the person with diabetes, but CGM may be the tool to help you learn how to adjust the amount, timing, and type of insulin delivery to match your food.
When you start to use CGM you will get new information to use. It is important that you understand some of the diabetes basics that you likely learned a while back. For example, just how long does it take for short-acting insulin to start working and how long does it last? You want to make sure you understand this before making changes in your diabetes care routine.
Why not take a refresher course on diabetes skills and concepts so you will be able to use the CGM information safely and to the fullest?
Take it slow
Expect it to take some time to get the most from CGM. Start by learning as much as you can about the "technical" aspects of your new CGM (insertion, wearing, features, etc). While that might seem complicated at first, it is the first step and you will learn all you need. It is essential to make certain you learn how to use the information. You will need to work closely with your health care provider (HCP) as you use the CGM information to help your diabetes care.
Be careful not to overreact to information at first. Don't be surprised if you have an emotional response to seeing all the glucose changes you have. Pictures and graphs can hit us hard in ways that numbers don't. Try not to tune out, but instead take the challenge to see how you can use this technology to help your diabetes care. Think positive! Although there is a lot of information, in a short time you will learn how to focus in and see the important trends in glucose.
If you are having questions and issues, don't keep them to yourself. Chances are you are not the only one with these questions, and you will need to address the questions to continue with CGM.
You may find you go through stages as you adapt to CGM, such as:
- Feeling so excited (but maybe you don't fully understand it yet)
- Starting to learn how to wear and insert sensors, push buttons, change settings, where to keep receiver, and figure this thing out
- Starting to learn about glucose trend information and know how to troubleshoot (be careful here- if you are having questions and issues, make sure you get help)
- Understanding the information and applying it to your diabetes self-care
- Continuing to learn and gain benefit
How Do Glucose Sensors Work?
This section is very important but it may be a little confusing at first. You may want to read quickly through this section, and then come back and read it at the end and again later.
The glucose sensors that are available at this time are small electrodes that are placed under the skin in the fatty tissue for a number of days. They go in the skin, using a spring insertion device (like a lancet device or infusion set inserter), with a needle helping the sensor get in, but only the small, comfortable sensor remains taped in place (similar to some insulin infusion sets). The process should not be painful.
The sensor produces a very small current that is actually the information about the amount of glucose in the body fluid around the sensor (interstitial fluid). The current rises when glucose rises. The current goes down when glucose goes down.
The sensor needs a number of hours to settle in to your body to give accurate glucose information. When it is ready, you do a calibration (check your finger BG and the CGM software uses the BG to determine what the measured current means in glucose values). You repeat the calibrations while wearing the sensor, according to the manufacturer's recommendation.
It is very important to calibrate carefully and correctly.
You must use your best blood glucose monitoring technique, including having clean, dry fingers, storing the strips properly, coding and using the meter correctly Remember: the sensor glucose information you get is only as accurate as the quality of the calibration you do.
It is best to calibrate when your glucose is not changing rapidly, because during times of rapid glucose change there may be a difference between the fingertip blood glucose and the glucose that is in your interstitial fluid.
You may not have thought much about this before, but the glucose is not always the same in all parts of the body. During fast glucose changes in the body, the interstitial glucose may be behind the blood glucose by about 10 minutes, perhaps less or more. (It is not possible to state exactly, as different circumstances may give different results.)
You can expect to see some differences between the sensor glucose and blood glucose. You can think of it as some little things adding up:
- the normal physiology (such as those glucose differences when the glucose is changing in the body)
- the time it takes for the CGM device to process the information (recognize the change in the interstitial fluid, collect that information, send it to the receiver for processing of the information).
- the accuracy of the meter BG calibration you did for the CGM (your technique, the meter itself, making sure the calibration gets immediately and accurately to the software for use)
Talk to your HCP about your questions about accuracy. Have realistic expectations about the information above. For example, if you looked at a 15% difference, then for a number of 100 mg/dl, 15% below is 85 and 15% above is 115 mg/dl.
Overall, with careful calibration and following instructions carefully, you will learn when the difference you may see is normal or if there is a problem and you need to troubleshoot (possible change sensor or address other problem). Make sure you report and concerns you have to your HCP and the manufacturer.
The first number of days (or weeks) will be for you to get started and begin to feel comfortable with CGM. Make sure you receive the necessary training to use your CGM properly and have a plan to work with your HCP for understanding and using the glucose information. Your goal at first may be to just get comfortable with this new diabetes device you have.
Remember all the general safety rules you follow still apply: Check your BG before making any diabetes care changes, including insulin correction doses. Check your BG before driving or doing anything that could be dangerous if you were low. Don't forget about ketones if you are high. Be careful not to take too many correction doses of insulin in too short a time period, as they can overlap and cause a low later. If you wear a pump, know when to change the infusion set and when insulin by injection is needed.
An Approach to Looking at CGM Information
You might find it helpful to think of looking at CGM information in three ways:
Immediate: The immediate approach includes using the glucose numbers, alarms, and trend information as they are happening. Confirm with a BG check before treating your diabetes. Here are a few examples to think about and discuss with your HCP.
- What does that number mean? You can look at a reading of 90 mg/dl and also learn if you are dropping/rising fast or more or less stable, and respond safely.
- What if you are about to eat and are on the high side and rising? More insulin? Wait and let the insulin dose get started?
- The low alarm goes off. Your BG shows 80 mg/dl. Your CGM shows that you are dropping. Even though 80 might not be considered "low," you may use the combination of the alarm, the trend, and the BG confirmation to treat with some carbohydrate.
- Your high alarm goes off. Your BG confirms that you are high but it is higher than the CGM value. You understand that this difference may be related to the differences in the body. The important thing is that you realize you forgot your bolus, didn't bolus the right amount for your carbs, etc. Have a plan on what to do about the high glucose alarm until your glucose comes down safely and slowly.
Do you follow the way you may approach things? You are now thinking about trends, events and diabetes care rather than just looking at point-in -time BG and CGM numbers.
Intermediate: This is how you respond after taking care of an immediate situation, such as described above. For example, if you just had a low and treated it and now feel better. Why not look back and see if you can figure out when the problem started, what may have caused it, how did you respond, and how did things work out? Maybe those insulin correction doses you took over the past 4 hours were too much and they overlapped.
Looking Back Long-Term: This approach involves looking at the glucose information from many days to see the big picture. It may be from download software or on your CGM itself. Focus in on certain days and compare day to day. How am I doing overall? What does the overnight time period look like? What usually happens after eating? When does hypoglycemia happen? Why are some days different than others? Focus in on patterns related to exercise, school/work, dining out, etc.
It may help to keep detailed written records for a few days to compare to your glucose download? Consider keeping a detailed food record for a few days and then bring it along with your CGM information to your appointment with your dietitian or clinician.
Lists Of Some Things To Think About and Discuss With Your HCP And Learn From CGM
- Insulin: How is the dose overall-enough/too much? Right timing, type, amount of long acting/basal insulin versus short acting (correction insulin dose, food bolus doses)? When is it safe to take another correction dose?
- Food: How do certain foods affect you? Do you know enough about the foods you eat? Is your meal insulin the right type, timing and amount? Insulin to carbohydrate ratio ok? Insulin before meals rather than during or after? How do different kinds of carbohydrates affect your glucose? Restaurant food versus home meals?
- Exercise: Short term: safety from lows. Longer term: prevent the highs and lows related to exercise. How much food to take right away? When to decrease or increase the insulin (temp basal if on pump). Do you see delayed lows from the exercise (overnight or next day)? How do different types of exercise affect you? When does your glucose rise from exercise?
- Hypoglycemia: When and how often does hypoglycemia happen? Focus in on one episode: What may have caused it? Do you recognize symptoms? How do you treat? What happened after your treated the low? Can you learn something from this episode that might help to prevent other lows? Do you recognize your lows?
- Schedule/routine: How are work/school/weekends different?
- Sick day management: how things are working (Don't forget all your sick day rules, including ketone monitoring!)
- Stress: How does stress affect your diabetes?
- Insulin pump: Use info to check your basal rate, insulin to carbohydrate ratio, insulin sensitivity. Are you making the most of all the features- special bolus features, temporary basal rates, etc? Are you changing your infusing set soon enough? Some unexplained high blood glucoses may indicate it's time to change the infusion set.
- Responding to CGM immediate information: You may be doing the best you can with the best treatment available. CGM may help you by giving you early warning of the glucose trends. Discuss your plan on how to respond to the CGM information as it happens.
A Special Word On Alarms
Finding the right alarm settings may take some time. Some HCPs may suggest that you start out for the first few days without glucose alarms or with the low glucose setting low and the high alarm setting high, so that you can just get used to wearing CGM. If your HCP recommends that you start this way, remember you are not going to get the value of these alarms at this time. After a short time you can start to adjust and find the best settings for you. The best setting for an alarm may not always be the actual glucose value you are considering. Move the settings up or down and reassess until you find the best setting. Night, day, school, work, may require a different setting. Expect to change settings and know when you may wish to silence them. Everyone is different here so work closely with your HCP.
If you are troubled by alarms, discuss the following with your HCP: What do the alarms mean to you? How often is too often and a nuisance to you, and when are the alarms good information? How can I find the best settings for me and my lifestyle? Are the alarms a message to focus on trying to fix a problem that keeps happening? Do I know how to adjust, silence, use vibrate, delay alarms (if features are available)?
Thinking about high and low glucose alarms settings, finding the best balance:
- Low alarm: the higher the number you set, the more alarms you may get when you are normal/low. The lower you set this, you may find fewer "nuisance" alarms but may not get enough warning for some lows. Work with your HCP for the best settings for you day/night and during your routine. This setting may be influenced by if you have awareness of hypoglycemia or not.
- High alarm: sometimes just after eating the interstitial glucose may be rising behind the blood glucose and if you put this setting too high, you may not get an early enough warning. If you set the alarm too low, the alarm may be going off every time you eat. After you wear CGM for a bit and make improvements in your postprandial glucose you may be able to lower the high alarm to give you earlier warning.
Skin/ Tape Issues
If you are having irritation/ redness underneath the tape or if the tape isn't sticking well, make sure to talk to your HCP. There are different tapes and skin wipes that you can try. Don't ignore the problem, as if you don't resolve it you will not want to use CGM. Your HCP has experience helping patients who use insulin pumps with similar questions, so even if CGM is new, he or she may have some good ideas. Call the manufacturer as well to report problems.
- Look at the glucose information frequently to learn as much as you can, but try to keep things in perspective. You may get more information this way, rather than only waiting for alarms.
- Aim for improvement, not perfection. Reduce the extremes in the glucose peaks and valleys. Step back and see the big picture. Fix small things, usually one at a time, and over time these small changes may make a big difference. If you don't know what to do first, try learning about and preventing some lows. Some people find that their overall diabetes control may improve after fixing some of the lows. Work with your HCP to make small changes, reassess, and make some more small changes.
- View the CGM information as more than a glucose number. CGM provides glucose trends and glucose events (highs, lows,). Focus on prevention and catching potential events early.
- Prevent alarm burnout by adjusting the alarm settings with help from your HCP.
- As your glucose control improves, you might find you are gaining weight - as your body is able to store this glucose instead of losing glucose in the urine. Talk to your HCP about this who will probably recommend a change in your food/insulin/exercise,
- Try not to get discouraged - remember it is still diabetes ... but now you have a wonderful tool to help you.
Published November 24, 2006
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