by Dr. Emil Katz
(Tel Aviv , Israel)
Question from Dr. Emil Katz:
I am 67 years old and exercise intensively every day. My morning glucose level has been 120–135 mg/dL for the last 10 years.
In the afternoon, 3–4 hours after lunch, my glucose level is below 100 mg/dL.
Can my normal fasting level simply be slightly outside the statistics, meaning my personal cut-off is not 126 mg/dL but perhaps 135 mg/dL?
A fasting glucose of 120–135 mg/dL should not be dismissed as “normal for you.” Fasting glucose from 100–125 mg/dL is usually in the prediabetes range, while 126 mg/dL or higher on repeat testing meets the diabetes range.
It is possible to have higher morning readings and normal afternoon readings. Common reasons include the dawn phenomenon, overnight liver glucose release, insulin resistance, dinner composition, sleep quality, stress, or timing of exercise.
The best next step is to review HbA1c, repeat fasting glucose, and possibly an oral glucose tolerance test or CGM pattern with your doctor.
Answer by Dr. Albana Greca, MD, MMedSc
Hi Dr. Katz,
Your question is thoughtful. Individual variation exists in biology, but diagnostic glucose thresholds are not meant to describe what feels normal for one person. They are used because risk of diabetes-related complications rises as glucose exposure increases.
Not necessarily. Many people have higher fasting glucose in the morning but lower glucose later in the day. This can happen because early-morning hormones tell the liver to release glucose. In people with insulin resistance or reduced insulin response, that glucose rise may not be fully controlled.
This is often called the dawn phenomenon. ADA also describes morning highs as commonly related to the dawn phenomenon or waning insulin effect.
I would be careful with that interpretation. A fasting value of 135 mg/dL is above the standard diagnostic threshold for diabetes if confirmed on repeat testing. A personal “normal” should not replace validated diagnostic ranges.
That said, one fasting glucose number should be interpreted together with HbA1c, repeat fasting tests, after-meal readings, symptoms, medication use, kidney function, anemia status, and overall cardiovascular risk.
You may compare values here: normal fasting blood sugar levels.
Your afternoon glucose below 100 mg/dL is reassuring, but it does not cancel out repeated high fasting readings. Intensive daily exercise can improve muscle glucose uptake and may explain lower later-day values.
The pattern may suggest isolated fasting hyperglycemia, dawn phenomenon, hepatic glucose output, or early insulin resistance. A CGM can be useful because it shows the overnight pattern, not only a single morning value.
You may also use this page: HbA1c to average glucose calculator.
Repeated fasting readings of 126 mg/dL or higher should be reviewed with a clinician. Do not ignore them because afternoon readings are normal. Diagnosis and treatment decisions should be based on confirmed laboratory results and overall risk.
Your lower afternoon glucose is encouraging, but fasting readings of 120–135 mg/dL deserve follow-up. I would not redefine 135 mg/dL as normal without checking HbA1c, repeat fasting glucose, and possibly CGM or oral glucose tolerance testing.
Educational safety note: This answer is for general diabetes education only. It does not replace personal medical advice, diagnosis, or treatment. Please discuss repeated fasting glucose above target with your healthcare provider.
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by PJV
Question from PJV:
My son recently was in South Africa and his blood sugar reading was 12.3. What does that convert to in USA terms please?
I think South Africa is the same as Canada.
A blood sugar reading of 12.3 mmol/L converts to about 221 mg/dL in USA terms.
The formula is simple: mmol/L × 18 = mg/dL. So, 12.3 × 18 = 221.4 mg/dL.
This is a high reading, but how serious it is depends on when it was checked: fasting, before a meal, after a meal, during illness, after travel, or after eating carbohydrates.
Answer by Dr. Albana Greca, MD, MMedSc
Hi PJV,
Yes, South Africa and Canada commonly use mmol/L for blood sugar readings, while the United States commonly uses mg/dL.
To convert from mmol/L to mg/dL, multiply by 18:
12.3 mmol/L × 18 = 221.4 mg/dL
So your son’s reading of 12.3 mmol/L is about 221 mg/dL in USA terms.
You can also use this tool: convert mmol/L to mg/dL.
Yes, 221 mg/dL is high for most situations. If it was a fasting or before-meal reading, it is clearly above the usual target range. If it was checked after eating, it is still above the common after-meal target for many people with diabetes.
However, one reading alone does not give the full picture. It matters whether your son has diabetes, what he ate, whether he was sick or stressed, whether he had been traveling, and whether the test was done fasting or after a meal.
You may compare readings here: blood sugar levels by time of day.
Read more here: blood tests for diabetes.
If your son has diabetes and his blood sugar is repeatedly high, he should contact his healthcare provider. If blood sugar is around 250 mg/dL or higher, especially during illness or with symptoms, ask the doctor whether ketones should be checked.
Seek urgent help for vomiting, dehydration, confusion, severe weakness, fast or deep breathing, chest pain, fruity-smelling breath, or moderate or large ketones.
A reading of 12.3 mmol/L equals about 221 mg/dL. This is high, but the meaning depends on timing and symptoms. The safest next step is to repeat testing, record the situation, and review persistent high readings with a doctor.
Educational safety note: This answer is for general diabetes education only. It does not replace personal medical advice, diagnosis, or treatment. Do not change diabetes medication or insulin based on one reading without speaking with a healthcare provider.
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by Alaima
Question from Alaima:
What is the emergency blood sugar remote monitoring system? Is it available only for hospital use, or can one have it at home?
Emergency blood sugar remote monitoring means using a blood glucose meter, continuous glucose monitor, smartphone app, or caregiver alert system to follow glucose levels outside the hospital.
Yes, many people can monitor blood sugar at home. Some use a regular glucose meter. Others use a continuous glucose monitor, also called a CGM, which can show glucose trends and may share alerts with a caregiver.
But remote monitoring does not replace emergency care. If blood sugar is dangerously high or low, the patient must follow a written diabetes safety plan and seek urgent medical help when needed.
Answer by Dr. Albana Greca, MD, MMedSc
Hi Alaima,
An emergency blood sugar remote monitoring system is not only for hospitals. Today, many people with diabetes can monitor glucose at home or while traveling using a glucose meter or a continuous glucose monitor.
Remote monitoring means checking blood sugar and sharing the information with the patient, caregiver, family member, or healthcare team. This may help detect high or low blood sugar earlier.
Common options include:
You may find this helpful: diabetes home testing.
A glucose meter checks blood sugar from a small drop of blood, usually from the finger. It gives one reading at that moment.
A CGM uses a small sensor under the skin to estimate glucose every few minutes. It can show whether glucose is rising, falling, or staying stable. Some CGMs can send alerts for low or high glucose and may allow sharing with another person.
Even if you use a CGM, your doctor may still advise finger-stick checks in certain situations, such as symptoms that do not match the CGM reading, rapidly changing glucose, or device problems.
Yes. Blood glucose meters are commonly used at home, work, school, and during travel. CGM systems are also used at home by many people with diabetes.
Home monitoring is especially helpful for people who use insulin, have frequent low blood sugar, have very high readings, live alone, are elderly, have children with diabetes, or need closer diabetes follow-up.
Some countries use mmol/L, while the United States commonly uses mg/dL.
Use this tool: convert mmol/L to mg/dL.
A diabetes emergency kit may include:
Important: fast-acting insulin should only be used if it is prescribed and the patient has clear instructions. It should not be used casually to “correct” high sugar without a medical plan.
Seek urgent medical help for confusion, fainting, seizure, chest pain, breathing difficulty, vomiting, dehydration, severe weakness, moderate or large ketones, or blood sugar that stays very high despite following your diabetes plan.
Read more here: dangerous blood sugar levels.
A glucose meter or CGM can warn you about high or low blood sugar, but it does not treat the emergency by itself. Make sure you have a written plan from your doctor for low blood sugar, high blood sugar, ketones, sick days, and when to go to the hospital.
Remote blood sugar monitoring can be useful at home, especially for people at risk of low or high blood sugar. The safest system is not only a device, but a full plan: accurate monitoring, correct interpretation, emergency supplies, caregiver support when needed, and clear instructions from your diabetes care team.
Educational safety note: This answer is for general diabetes education only. It does not replace personal medical advice, diagnosis, or treatment. Do not change insulin, diabetes medicine, glucose targets, or emergency treatment steps without speaking with your healthcare provider.
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