Continuous Glucose Monitoring

Lyle D. Haskell, D.P.M.

Using real-time glucose data to lower long-term complication risk

Why real-time glucose information matters

Glucose spikes and prolonged high glucose can occur without obvious symptoms. A continuous glucose monitor (CGM) displays your glucose trend throughout the day, helping you see how food, activity, sleep, stress, and medications affect you in real time.

Over time, elevated glucose can damage nerves and blood vessels. This raises the risk of progressive complications, including reduced sensation (neuropathy), slower healing, foot ulcers and infection, and in some cases significant foot and ankle deformity (Charcot changes).

This handout is educational and does not replace medical advice. Do not change prescription medications without your prescribing clinician.

Quick start: a 14-day CGM plan

• Wear your CGM continuously and keep it connected to your phone/app.

• For 14 days, write brief notes with time stamps: meals (what and rough portion), exercise, sleep quality, stress, and medications/supplements.

• Pick 1–2 small experiments: e.g., a 10–15 minute walk after dinner, or eating carbohydrates last.

• Review your patterns: when do you spike, how high, and how long does it take to come back down?

• Bring your CGM summary to your appointment so we can personalize targets and the plan.

Over-the-counter CGM option: Stelo (Dexcom)

Stelo is an over-the-counter CGM system available without a prescription. It is intended for adults (18 years and older) who are not using insulin. Stelo is worn on the back of the upper arm and is designed for up to a 15-day wear period. Note: You must have a “smart phone” and have downloaded the “Stelo App”, in order to record and read your glucose numbers and view your “real time” glucose graph.

Do not use Stelo if you have problematic hypoglycemia (low blood sugar) or if your clinician has told you that you need urgent low-glucose alerts. If you use insulin or have frequent lows, ask your clinician if the prescription device: Dexcom 7 CGM is more appropriate for you.

How to use CGM data (what to look for)

Focus on trends, not a single number. Helpful metrics include:

• Time in Range (TIR): the percent of the day your glucose stays in your target range. Many adults aim for at least 70% in range (your clinician may set a different goal).

• Post-meal peak: your highest value after eating (often 1–2 hours after the first bite).

• Time to recover: how long it takes to return toward your pre-meal level.

• Repeat patterns: consistent spikes after certain foods, at certain times of day, or after poor sleep/high stress.

• Effect of activity: how a short walk or strength session changes the glucose curve.

General glucose targets often used for many nonpregnant adults with diabetes include 80–130 mg/dL before meals and less than 180 mg/dL 1–2 hours after starting a meal. Your personal goals may differ.

When you see a spike, consider these practical moves:

• Take a 10–15 minute easy walk (if safe for you).

• At the next meal, emphasize fiber and protein first, and reduce refined carbs/sweets.

• Adjust portions (especially starches) and avoid sugary beverages.

• Review sleep, stress, and missed medication doses; discuss persistent patterns with your clinician.

Food choices, meal order, portion size, and timing

Meal order (carbohydrates last)

• Start with non-starchy vegetables (fiber).

• Then eat protein (and healthy fats).

• Finish with starches and sweets (carbohydrates last).

• Use CGM feedback: if your post-meal peak improves with this order, keep it.

Portion size

• Larger portions of starches/sweets typically cause larger and longer spikes.

• Pair carbohydrates with protein and fiber to slow absorption.

• Use your CGM to find the portion that keeps your curve flatter and returns toward baseline.

Timing

• Try to keep meal times fairly consistent.

• Late-night large meals often worsen overnight glucose and next-morning readings.

• Choose snacks that are higher in protein/fiber and lower in refined carbs when possible.

Exercise timing: use movement as a glucose tool

Physical activity can lower glucose and improve insulin sensitivity. Many people see the biggest benefit from light-to-moderate movement right after meals.

• After-meal walk: start within 10 minutes of finishing a meal. Walk for 10–15 minutes (or 3 short walks after breakfast, lunch, and dinner). Timing your walk immediately AFTER a meal encourages your muscles to “soak up” glucose rather than your pancreas needing to adjust for the elevated blood sugar on its own.

• Strength training: building muscle helps improve glucose control over time.

• If you take glucose-lowering medications, learn your personal pattern with your CGM and discuss safety with your clinician.

Sleep and stress: invisible drivers of glucose

Poor sleep and ongoing stress can increase insulin resistance and raise glucose. CGM data often shows higher readings after short or disrupted sleep, during illness, or during periods of emotional stress.

• Aim for 7–9 hours of sleep when possible and keep a consistent sleep schedule.

• Use brief daily stress tools: slow breathing, stretching, a short walk, or mindfulness.

• If you snore, have daytime sleepiness, or suspect sleep apnea, discuss evaluation and treatment with your clinician.

Supplements and meal add-ons that may help

Fiber (food first; supplements if needed)

• Fiber slows carbohydrate absorption and can reduce post-meal spikes. Emphasize vegetables, legumes/beans, nuts/seeds, and whole grains.

• If using a fiber supplement (e.g., psyllium), start low, increase gradually, drink plenty of water, and separate from other medications by at least 2 hours.

Timing of prescription medications

Do not change prescription medications without guidance. CGM data can help you and your clinician decide whether medication timing could be optimized.

• Take medications exactly as prescribed (many are designed for a specific time of day or to be taken with food).

• Use CGM patterns to identify: (a) fasting/morning highs, (b) after-meal spikes, and (c) overnight trends.

• Bring your CGM reports to appointments so your clinician can match treatment timing to your patterns.

• If you feel symptoms of low blood sugar or have repeated very high readings, follow your clinician’s plan and seek urgent care when appropriate.

Protecting your feet to prevent progressive damage and deformity

High glucose increases the risk of nerve damage and slow healing. Reduced sensation can make it easier to miss injuries. Early action prevents small problems from becoming major problems.

• Check your feet daily (tops, bottoms, between toes). Use a mirror if needed.

• Report any blister, cut, redness, drainage, or new pain immediately.

• Do not walk barefoot. Wear supportive shoes that fit well.

• If one foot becomes warm, red, swollen, or changes shape, call urgently (possible serious complication).

Important CGM caveats and safety notes

• CGMs measure glucose in interstitial fluid, which can lag behind a fingerstick blood glucose reading when glucose is changing quickly (lag can be up to about 15 minutes).

• If your CGM number does not match how you feel, confirm with a fingerstick meter and follow your clinician’s guidance.

• Pressure on the sensor (sleeping on it) can cause falsely low readings (“compression lows”).

• Skin irritation can occur. Keep the site clean and contact your clinician if redness spreads or you see signs of infection.

• Stelo is not designed for people with problematic hypoglycemia and may not be appropriate for insulin users who need urgent low-glucose alerts.

When to contact your clinician urgently

• Repeated very high readings or high readings with vomiting, dehydration, or confusion.

• Symptoms of low blood sugar (shaking, sweating, confusion, fainting) or recurrent low readings.

• A red, hot, swollen foot or ankle; new foot shape change; or an ulcer/wound that is not healing.

References

1. FDA. FDA clears first over-the-counter continuous glucose monitor (Dexcom Stelo). March 5, 2024. https://www.fda.gov/news-events/press-announcements/fda-clears-first-over-counter-continuous-glucose-monitor

2. Dexcom. Stelo indications for use (OTC iCGM). https://www.stelo.com/en-us

3. Dexcom. Stelo safety information (hypoglycemia and other precautions). https://www.stelo.com/en-us/safety-information

4. American Diabetes Association. CGM & Time in Range (TIR). https://diabetes.org/about-diabetes/devices-technology/cgm-time-in-range

5. American Diabetes Association. Checking your blood glucose (general targets). https://diabetes.org/living-with-diabetes/treatment-care/checking-your-blood-sugar

6. American Diabetes Association. Understanding blood glucose and exercise. https://diabetes.org/health-wellness/fitness/blood-glucose-and-exercise

7. Imai S, et al. Eating vegetables before carbohydrates improves postprandial glucose excursions. 2013. https://pmc.ncbi.nlm.nih.gov/articles/PMC3674531/

8. Diabetes Care. Three 15-min bouts of moderate postmeal walking and postprandial hyperglycemia. 2013. https://diabetesjournals.org/care/article/36/10/3262/30770/Three-15-min-Bouts-of-Moderate-Postmeal-Walking

9. Shishehbor F, et al. Vinegar consumption attenuates postprandial glucose/insulin: systematic review/meta-analysis. 2017. https://pubmed.ncbi.nlm.nih.gov/28292654/

10. Ostman E, et al. Vinegar supplementation lowers glucose and insulin responses after meals. 2005. https://pubmed.ncbi.nlm.nih.gov/16015276/

11. Gibb RD, et al. Psyllium fiber improves glycemic control in type 2 diabetes: meta-analysis. 2015. https://www.sciencedirect.com/science/article/pii/S0002916523272354

12. ADCES. CGM glossary: lag time (interstitial vs fingerstick). https://www.adces.org/education/danatech/glucose-monitoring/continuous-glucose-monitors-(cgm)/cgm-101/cgm-glossary/lag-time

13. American Diabetes Association. Foot complications (neuropathy and foot risk). https://diabetes.org/about-diabetes/complications/foot-complications

14. AAOS OrthoInfo. Diabetic (Charcot) Foot. https://orthoinfo.aaos.org/en/diseases--conditions/diabetic-charcot-foot/

15. UCSF Diabetes Teaching Center. Blood glucose & stress in diabetes. https://diabetesteachingcenter.ucsf.edu/blood-glucose-stress-diabetes

16. ADCES. Dexcom G7 and Stelo differences (wear time notes). https://www.adces.org/education/danatech/glucose-monitoring/continuous-glucose-monitors-(cgm)/cgm-selection-training/dexcom-g7-and-stelo-differences