A continuous glucose monitor (CGM) estimates your glucose, also called blood sugar, every few minutes and keeps a record, so you can see where your level is now and how it has moved over hours or days. NIDDK, part of the National Institutes of Health, explains that the sensor estimates glucose in the fluid between your cells, a level that is very similar to your blood glucose. Below you will see how that differs from a finger-stick meter, what Medicare says about cost, and what to check before you decide whether a CGM fits.
What does a continuous glucose monitor measure?
A CGM measures glucose in the fluid between your cells and turns that into an estimate of your blood glucose. NIDDK’s CGM overview describes three parts: a tiny sensor placed under the skin, often on the belly or arm, held in place by a sticky patch; a transmitter that sends the readings without wires; and a software program on a smartphone, an insulin pump or a separate receiver.
NIDDK sorts CGMs by how they show data. Real-time devices send and display readings automatically. Intermittent-scan devices estimate glucose continuously, but you scan them every few hours to view and store the data. A third type records data for your doctor to download and review later, and you wear it for a limited time.
How does a CGM differ from a finger-stick meter?
The main difference is what is read and how often. Harvard Health Publishing describes the finger-stick method as pricking a fingertip, placing a drop of blood on a test strip, and using a machine to read the blood sugar level. That gives you one reading each time you test. A CGM keeps estimating glucose over time, as the table shows.
| Question | Finger-stick meter | Continuous glucose monitor |
|---|---|---|
| What is read | Blood from a fingertip, placed on a test strip | Glucose in the fluid between cells, estimated (NIDDK) |
| How often | Each time you test | Every few minutes, stored over time (NIDDK) |
| What you see | A single number at the time of the test | Trends, and whether your level is rising or dropping and how fast (NIDDK) |
| Finger sticks | Every reading is a finger stick | Fewer are needed, though some checks are still recommended (NIDDK) |
NIDDK lists fewer finger sticks and fewer low blood glucose emergencies as benefits of a CGM compared with a standard blood glucose meter. It also says the people who gain the most use a CGM every day or nearly every day.
When do I still need a finger-stick check?
NIDDK says you may need to compare CGM readings with a finger-stick test and a standard blood glucose meter if you doubt the CGM’s accuracy, if you are changing your insulin dose, or if the CGM gives a warning alert. For some models, a finger-stick test is also used to calibrate the system. NIDDK notes that researchers are working to make CGMs more accurate and easier to use.
Each model’s labeling sets who may use it and at what ages. NIDDK says doctors can prescribe CGMs for adults and children, and some models can be used for children as young as 2. Check the label of the exact model you are considering for its approved age range and uses.
Can a CGM be used for type 2 diabetes without insulin?
NIDDK says your doctor may recommend a CGM if you need insulin to manage type 1 diabetes, type 2 diabetes or another form of diabetes. Medicare’s coverage rule is narrower. As of October 14, 2026, Medicare.gov’s continuous glucose monitor page says Medicare may cover a CGM and related sensors if you have diabetes, your provider orders it, you take insulin or have a history of problems with low blood sugar (hypoglycemia), and you or your caregiver have had enough training to use it as directed. If you do not take insulin, ask your clinician whether your low blood sugar history meets that condition.
A 2024 CGM meta-analysis on PubMed pooled 14 randomized controlled trials of adults with type 2 diabetes, including 825 people in 9 trials of real-time CGM and 822 in 5 trials of flash CGM. Its main finding was a modest but statistically significant reduction in HbA1c of about 0.32%, with moderate certainty. The authors noted that the trials were relatively short and that few reported adverse events, emergency department use or hospitalization. For what randomized trials can and cannot show, see Randomized Controlled Trials Explained (our research library).
Does a CGM help people without diabetes?
Harvard Health Publishing’s August 1, 2024 article says there are relatively few studies of CGMs in people who do not have diabetes, and that at this time there is no solid research showing their value for that group. The article’s author thinks value might appear in people with risk factors such as being overweight, having prediabetes or having a family history of diabetes, but says that would need to be scientifically established first. The article also notes that CGMs can be expensive and are not always covered by insurance.
How is a CGM placed on the body, and what are the downsides?
NIDDK describes a sensor inserted under the skin, often on the belly or arm, and held by a sticky patch. Harvard Health Publishing describes the sensor as one that painlessly pushes into the skin. NIDDK names the belly and arm as common sites; it does not say a specific site is required. The downsides NIDDK lists are below.
| Issue | What NIDDK says |
|---|---|
| Sensor replacement | Disposable sensors are replaced every 7 to 14 days, depending on the model. Some implantable sensors can last up to 180 days. |
| Transmitter and connection | Some transmitters may need replacing. You may need to reconnect the CGM, transmitter and receiver or smartphone if the CGM is not working correctly. |
| Skin | Redness or irritation from the sticky patch may occur for some people. A doctor can suggest techniques or medicines to help. |
| Accuracy | Finger-stick checks may be needed, as described above. |
| Cost | A CGM costs more than a standard glucose meter, though it may be covered by health insurance. |
What does a CGM cost, and what does Medicare cover?
As of October 14, 2026, Medicare.gov says Medicare may cover a continuous glucose monitor and related supplies as durable medical equipment under Part B. The page lays out the costs below. This is information, not legal advice.
| Cost item | What Medicare.gov says |
|---|---|
| Deductible | You pay after you meet the Part B deductible |
| Your share | 20% of the Medicare-approved amount, if your supplier accepts assignment |
| Non-participating supplier | It may charge you more. For rentals, the supplier must accept assignment for all rental months, or you pay the full cost up front and Medicare pays you later for its share. |
| Amount you could owe | Depends on your other insurance, how much your doctor charges, whether your doctor accepts assignment, the type of facility, and where you get it |
| Dollar amount | Not listed on the Medicare page; ask the supplier for an itemized quote |
Ask whether the supplier participates in Medicare or will accept assignment before you get the equipment, as Medicare.gov advises. Prices and bundles change, so check current pricing directly with the supplier.
Which CGM model fits, and what should I ask first?
NIDDK groups CGMs by how they show data rather than by brand, so this page does not compare models. Bring these questions to your clinician or supplier:
- Do I take insulin, or have I had low blood sugar episodes that Medicare’s condition describes?
- What is the exact model, and what age range and uses does its label cover?
- Will my plan cover it, and does the supplier participate in Medicare and accept assignment?
- Can I get an itemized quote before I agree to anything?
If a referral is part of this, Preparing Information for a Primary Care Referral explains what to bring.
Next step: Write down whether you take insulin and any low blood sugar episodes you have had, then use the New or Changed Prescription Questions Guide to prepare your questions for your next appointment.
By the Primary Care Visit Guide Team
Leave a Reply