Question 1

What is a continuous glucose monitor (CGM)?

Accepted Answer

A CGM is a wearable device that continuously measures glucose levels in the fluid just under your skin (interstitial fluid). It consists of a tiny sensor inserted under the skin, a transmitter that sends data wirelessly, and a receiver or smartphone app that displays your readings. Unlike finger-stick testing that shows a single point in time, CGM provides readings every 1-5 minutes along with trend arrows showing if glucose is rising, falling, or stable.

Question 2

Do I need a prescription to get a CGM?

Accepted Answer

For medical-grade CGMs designed for diabetes management (Dexcom G6/G7, FreeStyle Libre, Guardian), yes - you need a prescription from a healthcare provider. However, over-the-counter CGMs for general wellness (like Dexcom Stelo and Abbott Lingo) are now available without a prescription. These OTC options are designed for people who don't have diabetes but want to track their glucose for health optimization.

Question 3

How much does a CGM cost?

Accepted Answer

CGM costs vary widely depending on insurance coverage and which system you choose. With insurance, you might pay $0-75 per month out of pocket. Without insurance, costs can range from $75-400+ per month. FreeStyle Libre is generally the most affordable, while Dexcom tends to be more expensive but offers features like predictive alerts. Many manufacturers offer patient assistance programs for those who qualify.

Question 4

Which CGM is best for me?

Accepted Answer

The best CGM depends on your specific needs: Dexcom G7 offers the best accuracy (8.2% MARD), shortest warmup (30 min), and widest AID compatibility. FreeStyle Libre 3 is the smallest and most affordable with 14-day wear. Guardian 4 integrates exclusively with Medtronic pumps. Eversense is implantable for 6-month wear if you dislike frequent sensor changes. Discuss with your healthcare provider based on your insurance, diabetes type, and whether you use an insulin pump.

Question 5

Does inserting the CGM sensor hurt?

Accepted Answer

Most people describe sensor insertion as a quick pinch that's less painful than a finger stick. Modern applicators insert the sensor very quickly using a spring-loaded mechanism. The needle is thin (typically 26-28 gauge) and only briefly enters the skin to place the sensor wire. After insertion, you shouldn't feel the sensor during normal wear. Some areas are more sensitive than others - the arm tends to be less painful than the abdomen for many users.

Question 6

Where should I wear my CGM sensor?

Accepted Answer

FDA-approved sites vary by device: Dexcom G7 is approved for the abdomen (ages 2+) and back of upper arm (ages 18+). FreeStyle Libre is approved for the back of the upper arm only. Many users successfully wear sensors on other sites like thighs or lower back, though this is off-label. Choose a site that's not frequently compressed, has adequate subcutaneous fat, and where you can comfortably reach for insertion.

Question 7

Can I shower, swim, or exercise with my CGM?

Accepted Answer

Yes! Most CGMs are water-resistant and designed for active lifestyles. Dexcom G7 and FreeStyle Libre 3 are water-resistant for 30 minutes at 1 meter depth (showering, brief swimming). However, prolonged water exposure can loosen adhesive. For swimming or sweating, consider using overtapes or adhesive patches. The transmitter should stay attached during water activities - just pat dry afterward.

Question 8

How accurate are CGM readings?

Accepted Answer

Modern CGMs achieve 7-10% MARD (Mean Absolute Relative Difference), meaning readings are typically within 7-10% of lab values. Dexcom G7 has 8.2% MARD, FreeStyle Libre 3 has 7.9% MARD. Accuracy is generally best when glucose is stable and in the normal range. Readings may be less accurate during rapid glucose changes, the first 24 hours after insertion, or with compression (sleeping on sensor). All current iCGM systems are approved for making insulin dosing decisions without confirmatory finger sticks.

Question 9

Why does my CGM reading differ from my finger stick?

Accepted Answer

CGM measures glucose in interstitial fluid, while finger sticks measure blood glucose. There's a natural 5-15 minute 'lag time' as glucose moves from blood to interstitial fluid. This difference is most noticeable when glucose is rapidly rising or falling. Additionally, finger stick accuracy can be affected by hand washing, sample size, and meter accuracy. If readings differ significantly (>20%) when glucose is stable, consider recalibrating (if supported) or contacting the manufacturer.

Question 10

How do I prevent 'alarm fatigue'?

Accepted Answer

Start by setting realistic thresholds - if you're frequently going above 180 mg/dL, setting your high alert at 180 will cause constant alarms. Consider starting with wider thresholds (e.g., 250 high, 70 low) and gradually tightening as your control improves. Use the 'urgent low' alert at 55 mg/dL and keep this one enabled. Some users set different alert schedules for day and night. Remember that ignoring all alerts defeats the purpose of CGM.

Question 11

What are predictive alerts?

Accepted Answer

Predictive alerts warn you before you reach high or low glucose thresholds, giving you time to act. For example, the 'Urgent Low Soon' alert on Dexcom predicts when glucose will drop below 55 mg/dL in the next 20 minutes. This early warning allows you to treat a low before it becomes severe. Predictive alerts are especially valuable during sleep or exercise when you might not notice symptoms.

Question 12

Can my family see my CGM readings?

Accepted Answer

Yes! Most CGM systems offer data sharing features. Dexcom Follow and LibreLinkUp apps allow up to 10 followers to see real-time glucose data and receive their own alerts. This is especially valuable for parents of children with diabetes, caregivers of elderly patients, or anyone who wants a safety net. Followers can see current readings, trend arrows, and set their own alert thresholds. Sharing requires an internet connection on both devices.

Question 13

Why am I getting 'compression lows' at night?

Accepted Answer

Compression lows (PISA - Pressure-Induced Sensor Attenuation) occur when you sleep on your sensor, restricting blood flow and glucose transport to the sensor area. The CGM shows falsely low readings that recover when you move. Solutions include: wearing the sensor on your non-dominant sleeping side, using your arm instead of abdomen, sleeping on your back, or using a sensor overpatch to distribute pressure. Some users set their low alert slightly lower at night to account for this.

Question 14

My sensor keeps falling off. What can I do?

Accepted Answer

Several strategies can improve sensor adhesion: Clean the site with alcohol and let it fully dry before insertion. Use a skin prep product like Skin Tac or IV Prep before applying. Add an overtape or adhesive patch on top (many brands are available, or manufacturers sometimes provide free patches). Avoid applying to areas that flex a lot or get sweaty. Consider a different body site if one location consistently fails. Store sensors at room temperature - cold sensors may not adhere as well.

Question 15

What does 'Sensor Error' mean?

Accepted Answer

Sensor errors indicate the CGM cannot provide accurate readings. Common causes include: dehydration affecting interstitial fluid, bleeding at the insertion site, sensor hitting a blood vessel or scar tissue, extreme temperatures, or the sensor becoming dislodged. Wait 15-30 minutes to see if it resolves. If errors persist, you may need to replace the sensor. Contact the manufacturer for a replacement if the sensor fails before its expected life - most have generous replacement policies.

Question 16

How do I deal with Bluetooth connection problems?

Accepted Answer

CGM Bluetooth issues are common but usually fixable. Keep your phone within 20 feet of the sensor. Check that Bluetooth is enabled and the CGM app has Bluetooth permissions. Restart both your phone and the app. Ensure you're running the latest app version. Remove other Bluetooth devices that might interfere. For Dexcom, only pair with one display device at a time (phone OR receiver, not both simultaneously reading the transmitter). If problems persist, try unpairing and re-pairing the sensor/transmitter in the app.

Question 17

What is automated insulin delivery (AID)?

Accepted Answer

Automated Insulin Delivery (AID), also called 'closed-loop' or 'artificial pancreas,' combines a CGM with an insulin pump and a control algorithm that automatically adjusts insulin delivery based on glucose readings. Current systems are 'hybrid' closed-loop, meaning they handle basal adjustments automatically but still require you to enter meal boluses. AID can significantly improve Time in Range and reduce hypoglycemia, especially overnight.

Question 18

Which CGMs work with which insulin pumps?

Accepted Answer

Compatibility varies: Dexcom G6/G7 works with Tandem Control-IQ, Omnipod 5, and Beta Bionics iLet. FreeStyle Libre is currently compatible with Omnipod 5 (upcoming), and Ypsomed's mylife Loop. Guardian 4 works exclusively with Medtronic 780G. If you're considering an AID system, check current compatibility as it changes frequently. Some users choose CGMs based on their preferred pump, while others select pumps based on their preferred CGM.

Question 19

What is DIY looping?

Accepted Answer

DIY Loop refers to open-source AID systems created by the diabetes community, including Loop, OpenAPS, and AndroidAPS. These systems are not FDA-approved but are used by thousands worldwide. They typically offer more customization than commercial systems. Building a DIY system requires technical knowledge, compatible hardware (older Medtronic pumps or RileyLink for Omnipod), and understanding that you're responsible for your own outcomes. The community provides extensive documentation and support.

Question 20

Can I use a CGM during pregnancy?

Accepted Answer

Yes, CGM use during pregnancy is increasingly recommended. Dexcom G6/G7 is specifically FDA-approved for use during pregnancy. Studies show CGM helps pregnant women with diabetes achieve better glucose control and improved outcomes. The tight targets during pregnancy (typically 63-140 mg/dL) make CGM especially valuable. However, interstitial fluid glucose may behave slightly differently during pregnancy, so work closely with your healthcare team.

Question 21

What do I do about my CGM before an MRI?

Accepted Answer

You must remove your CGM sensor before an MRI, CT scan with contrast, or diathermy treatment. The metal components can cause burns, and the magnetic field can damage the sensor. Remove the sensor before the procedure and insert a new one afterward. Contact your CGM manufacturer for replacement sensors if the procedure caused early removal. Some X-rays may be safe - check your specific device's labeling or contact the manufacturer.

Question 22

Can I travel with my CGM?

Accepted Answer

Yes, CGMs are designed for travel. TSA allows CGMs through security - inform agents you're wearing a medical device. You may request a pat-down instead of full-body scanner if concerned, though most users go through scanners without issues. Airport X-ray machines for carry-on luggage are safe for sensors and transmitters. Bring extra supplies and carry them in your carry-on (not checked baggage). For international travel, bring your prescription and a letter from your doctor in case of customs questions.

Question 23

Are there medications that interfere with CGM readings?

Accepted Answer

Modern iCGM systems (G6/G7, Libre 3) have resolved most interference issues, including acetaminophen (Tylenol) which affected older sensors. However, some medications can still interfere: hydroxyurea (for sickle cell) causes false highs; vitamin C in very high doses may affect readings; and some dialysis solutions can interfere. Always check your specific CGM's prescribing information. If you're on these medications, discuss with your healthcare provider whether additional finger-stick verification is needed.

Question 24

Can I sell my unused CGM supplies?

Accepted Answer

Yes, selling your unused, unexpired CGM supplies is legal and helps others access affordable diabetes care. Many people have extra supplies due to prescription changes, switching devices, or stockpiling. These are your personal property. Supplies must be sealed in original packaging, unexpired (preferably with 6+ months remaining), and in good condition. Popular items include Dexcom sensors and transmitters, FreeStyle Libre sensors, and Guardian sensors.

Question 25

How much are my unused CGM supplies worth?

Accepted Answer

The value of CGM supplies depends on the brand, type, quantity, and expiration date. Dexcom G6/G7 sensors typically command higher prices due to demand. Supplies with longer expiration dates (12+ months) are worth more than those expiring soon. Transmitters, receivers, and unopened sensor boxes are all valuable. Check our price list for current estimates, or contact us for a personalized quote on your specific supplies.

Question 26

Why do people sell their CGM supplies?

Accepted Answer

Common reasons include: switching to a different CGM system, insurance changing coverage, overstock from prescription changes, doctor prescribing more than needed, supplies received as samples, or sadly, a loved one passing away. Rather than letting supplies expire and go to waste, selling them helps others who struggle to afford CGM technology while putting money back in your pocket.

Frequently Asked Questions

Getting Started

Using Your CGM

Alerts & Alarms

Technical Issues

Insulin Pumps & AID

Special Situations

Selling & Costs

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