Fluctuation of glucose level

by Mathi
(India)




Question from Mathi

Hi Doctor. My fasting glucose level is 167 mg/dL, but after a workout my random glucose level is 114 mg/dL. I have type 2 diabetes and I am 60 years old. Why does my glucose fluctuate like this?


Quick Answer




Mathi, a drop from 167 mg/dL while fasting to 114 mg/dL after exercise can happen because physical activity helps your muscles use glucose for energy and usually improves insulin sensitivity. The 114 mg/dL result after your workout is reassuring, but it does not cancel out the fasting reading of 167 mg/dL.


For many adults with diabetes, a fasting or pre-meal glucose target is around 80–130 mg/dL, although your personal target may be different. Repeated fasting readings around 167 mg/dL suggest that your overall diabetes treatment should be reviewed.


Answer by Dr. Albana Greca, MD, MMedSc



Hello Mathi,



The difference between your two readings is not unusual in someone with type 2 diabetes. However, the two numbers were taken under very different conditions, so they should not be compared as though they were the same type of glucose test.



Why Is Your Fasting Glucose 167 mg/dL?



A fasting glucose of 167 mg/dL is above the usual target for many adults with diabetes. Several factors can contribute to higher glucose in the morning, including glucose released by the liver overnight, insufficient insulin action, the timing or amount of your evening meal, poor sleep, stress, illness, and whether your diabetes medicine is controlling glucose throughout the night.



Some people with type 2 diabetes also experience the dawn phenomenon. In the early morning, hormones such as cortisol and growth hormone can signal the liver to release glucose, causing blood sugar to rise before breakfast.



Why Did Exercise Lower It to 114 mg/dL?



During physical activity, your working muscles need energy and can take up more glucose from the bloodstream. Exercise can also improve how effectively your body responds to insulin. As a result, blood glucose often falls during or after a workout.



Therefore, seeing your glucose decrease from 167 to 114 mg/dL after exercise can be a normal and beneficial response to physical activity. Regular exercise is an important part of managing type 2 diabetes.



How Should You Interpret These Numbers?



The important point is that fasting and post-exercise readings tell us different things. Here is how I would interpret your results:



















ReadingResultMeaning
Fasting167 mg/dLAbove the usual target for many adults with diabetes
After workout114 mg/dLA good glucose level, likely influenced by exercise


For many nonpregnant adults with diabetes, a commonly used target is 80–130 mg/dL before meals and below 180 mg/dL after meals. These targets should be individualized according to your health, medications, duration of diabetes, and risk of low blood sugar.



Does 114 mg/dL Mean Your Diabetes Is Well Controlled?



It is a good reading, but one post-exercise result cannot show your overall diabetes control. Exercise may temporarily lower glucose even when your fasting levels are regularly too high.



For this reason, I would pay more attention to the pattern of your readings and your HbA1c rather than to one isolated measurement.



Check Your HbA1c



HbA1c gives a broader picture of your average glucose during approximately the previous two to three months. For many adults with diabetes, an HbA1c below 7% is a common goal, but at age 60 your target should still be individualized according to your overall health and treatment.



If your fasting readings frequently remain around 160–170 mg/dL or higher, I recommend discussing your glucose record and HbA1c with your doctor. Your meal plan, medication dose or timing, activity level, and other factors may need to be reviewed.



How to Monitor Your Glucose More Usefully



Instead of comparing readings taken under completely different conditions, try recording them at consistent times:




  • Fasting, before breakfast.

  • Before exercise when appropriate.

  • After exercise occasionally to understand your response.

  • Before meals when advised.

  • About 1–2 hours after the start of a meal when checking post-meal glucose.



Also record your meals, exercise, and medications. After several days, this can reveal patterns that are much more useful than a single reading.



Exercise Is Helpful, but Watch for Low Blood Sugar



Continue being physically active if your doctor has advised that exercise is safe for you. However, exercise can sometimes lower blood glucose too much, particularly if you use insulin or certain diabetes medicines such as sulfonylureas.




Important: If you take medicine that can cause hypoglycemia, ask your doctor whether you should check your glucose before and after exercise. A glucose reading below 70 mg/dL is considered low and should be treated promptly.


The Bottom Line



Mathi, your glucose falling from 167 mg/dL fasting to 114 mg/dL after exercise is understandable because physical activity helps remove glucose from the bloodstream. The post-workout reading is good, but your fasting value remains higher than the usual target.



I would continue regular physical activity, monitor your glucose at consistent times, and check your HbA1c. If fasting readings repeatedly remain around 167 mg/dL, discuss them with your doctor so your diabetes management can be adjusted if necessary.



Last medically reviewed: August 2026




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