Son wore a CGM for a week - scary results!

My 25-year old son has had hypoglycemia symptoms for years and recently got the chance to use a CGM cast off from a friend to see if he was actually having measurably low blood sugars.

Over the week, he learned that he was definitely having low blood sugar, set off the urgent low alert (<40mg/dl) twice in fact. And lots of high blood sugars too. The first few days he had a cold and his numbers were quite high, fasting around 150, high 200s/low 300s after meals. Then the cold cleared up, and his BG plummeted. Fasting of 70, and those urgent lows. Then after about a day or so of that, it went back up, fasting around 115 and post-meal between 150 and 250 generally. Played a competitive game of soccer without eating anything for hours before, BG 220 at the end of the game. GMI (estimated a1c) was 6.3. So, not at all normal.

He hates feeling low and complains of fatigue a lot, even though he is maintaining his high level of physical activity.

He has not seen a doctor yet, been a couple weeks since the CGM experiment.

I’m hoping you good and knowledgeable people will have some advice about what to do when he does finally see a doctor. How do you get a good diagnosis and possibly even treatment at an early stage? And does anyone know anything about the drug that can delay onset?

Thank you from a worried mom.

It looks like he does have some kind of issue. But it would be hard to know what yet. It could be type 1, type 2 or Mody or???

Medication can cause drops and worsen ones you already have, so not the solution I would pick, at least at first. Make sure you take a copy of the graph to the doctors for them to see. Some “normals” have some wild fluctuations, but going too low or going up to 300 is not normal. 70 is really not an abnormal level, but a finger stick should accompany it as CGM’s can be 20 points plus off.

Your body will release glucose into the system when you do hard exercise to supply it fuel, hence BG level reading higher after. A “normal” produces insulin to be actually able to use it. When you get sick your blood sugars will go up and be more erratic. They believe now that a virus can set off the process of becoming a diabetic. Covid is one of those viruses.

You will want an A1c, but also importantly a C-Peptide test and type 1 antibody tests. C-Peptide measures how much insulin you are producing. Low or low normal is a sign of type 1, because you aren’t producing enough insulin. High or high normal is a sign of type 2 because you are insulin resistant and producing more insulin to make up for it. An antibody test if positive is a sign of type 1, but some type 1’s test negative and they don’t know why.

I have no idea what is going on or which he is, but I would ask for both tests as over 35% of the time a type 1 is misdiagnosed as a type 2. When you get type 1 as an adult it has a tendency to be slower progressing and can take many years to fully happen. So it can be deceiving as you still produce some insulin and erratically for a while. Type 2 is much more common than type 1. But you need to know which you are dealing with for the proper treatment.

Type 2 can usually be controlled by diet and exercise. Maybe medication. But it is a metabolic disease that athletes and skinny people get too. Type 1 you lose the ability to make insulin and will have to have it at some point. There are several professional athletes that are type 1, you just have to make some adjustments for it. Eric here runs marathons and I go snorkeling out in the ocean for hours at a time. Not wanting to know, which prevents some people going to the doctor is the best way to end up really sick at some point what ever is going on. It could be as simple as changing how/what he eats if he’s a type 2.

  1. C-Peptide While most tests check for antibodies, this test measures how much C-peptide is in a person’s blood. Peptide levels typically mirror insulin levels in the body. Low levels of C-peptide and insulin can point to T1D
  2. Glutamic Acid Decarboxylase Autoantibodies (GADA or Anti-GAD)
    This test looks for antibodies built against a specific enzyme in the insulin-producing pancreatic beta cells.
  3. Insulin Autoantibodies (IAA)
    This tests looks for the antibodies targeting insulin
  4. Insulinoma-Associated-2 Autoantibodies (IA-2A)
    This test looks for antibodies mounted against a specific enzyme in
    beta cells. Both the IA-2A and GADA tests are common T1D antibody tests.
  5. Zinc Transporter 8 (ZnT8Ab)
    This test looks at antibodies targeting an enzyme that is specific to beta cells.
  6. Islet Cell Cytoplasmic Autoantibodies (ICA)
    Islet cells are clusters of cells in the pancreas that produce hormones,
    including insulin. This test identifies a type of islet cell antibodies present in up to 80 percent of people with T1D.

Thanks so much for all that helpful information! I will make sure my son brings it to his doctor’s appointment, whenever that happens.

FYI, he calibrated the dexcom with a meter multiple times and they were always within a point or two.

Reading over others’ posts in the forum, it seems that getting the correct diagnosis isn’t always straight forward for adults, which is worrying.

I think you might be right about Covid…he had it about 6 months ago and has definitely had less energy ever since. The hypoglycemic feelings have been bothering him for years, but maybe Covid destroyed more of his beta cells.

Thanks so much for taking the time to respond. And always happy to hear about athletic pwd given how important sports and being active is to him. :heart:


Having wonky numbers when sick is not unusual. When the body is fighting off an illness, it often releases glucose to help provide energy for the fight but with T1D, there is no corresponding release of insulin, so the number goes high (in T2D, the insulin release is not sufficient). Post illness one can go low due to increase in insulin doses to combat the highs (again T1D).
Exercise is a devil. When I (T1D) biked to work in the AM, I would need to dose pre-ride - morning exercise augmented my normal release of glucose at that time. Come the PM ride home - totally different story. Your son will have to learn what exercise does and also look at the time of exercise. It is a learning process.
Bring the CGM data with him and any logbook of exercise, illness, food. I know of no drugs that will delay T1D, though there is some data showing that adult onset of T1D, early use of insulin preserves some of the beta islet cells a bit longer. Not as aware of T2D treatments, so can’t comment.
See: – should answer a lot of your questions.

This is an interesting post. I’ll stay tuned for updates.

He should probably bring finger sticks to his appointment. (if he can stand to do it.) He can buy a machine at Walmart and strips to put in it for $40. He needs a machine anyway so that when he feels weak, he can test and see if he needs to eat a snack.

He could test his BG 4 times per day and write down what he was eating & activity levels. That would be useful for the Doc. If he did that for 2 weeks before his appointment, that would be superb. He should test when he wakes up in the morning, before meals, and anytime he doesn’t feel well. That will help him know how blood sugar impacts how he feels. It will help him understand how to feel better, long term.

Here’s how you check your blood sugar:

Stay in touch! Feel free to invite your son to talk to us if he has questions.

I’m pretty certain that they think that covid increased the incidence of type 1 diabetics. So, that’s an interesting twist on this tale. You might be the first person who has brought this up on the forum. You have enough problems right now, but I’ll leave this for the others to mull over because there has always been a poorly understood relationship between incidence of flu virus and the incidence of type 1 diabetes diagnoses.


Don’t worry too much, Mom. It sounds like you are surrounded by some very smart, very proactive 25-year olds. Good for them for having the initiative to collect the data and evaluate it. That’s really great! Their on to something. That initiative might lead to a diagnosis or better understanding of what’s going on so that your son has a better quality of life. I’m really impressed.

Your son should go to a PCP and not delay. I don’t mean to be too alarming, but medical problems are like potholes, they never get smaller on their own. There are a variety of things that can cause these symptoms, some simple and others not so simple. In addition to the above tests suggested by Marie20, he should get his thyroid checked. His PCP should refer him to an endocrinologist/diabetologist, preferably one at a med school, as they can run many tests in the clinic. And if he needs to see other specialist he can get a faster referral.

It helps also to have someone go with him to take notes, and help advocate for him.


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Good points, Mike!

Re-reading the OP, I have some additional suggestions. He should avoid sugar and simple carbs: his pancreas could be reacting by over secreting insulin, followed by stress hormones sending him high (which can also cause fatigue). He should eat more protein.
Another thought, if he is going down to 40, it may not be a good idea for him to drive. That is hard, but is serious, and needs to be considered.

I really really appreciate all of your suggestions. My son is seeing a primary care doctor tomorrow! Finally! I passed on all of your good advice and hopefully they will see whether this is the beginning of Type 1, or something else.

He is planning to show the CGM results to the dr and ask about antibody testing. I’m hoping he’ll let them know that he wants to find a way to avoid the highs and the lows, and to stop feeling so run down.

@MikeR1 Thanks for sharing your thoughts. As for the driving thing, he luckily has his life set up so he doesn’t do much driving. The two serious lows he had were when he was doing serious physical exertion (summiting a high peak) and right after being sick when I assume his pancreas overreacted after being high as @biosafety-guy mentioned. So I don’t think it’s a usual worry.

Anyway, really hoping the doctor is knowledgeable and helpful. And I’ll post again when we get some results!


Okay, nothing much to report yet. Son couldn’t remember the labs that the dr said she was ordering, but he thinks it might have included antibody and c-peptide. He did remember iron, electrolytes and an a1c.

But, wanted to report on one thing she told him that seems so strange to me…she said she was only worried about the highs he got, not the lows. She said lots of non-diabetics get low readings. Can that be true? Do people really get blood sugars below 40 that make them feel nauseous and sweaty?? I just don’t think I’ve ever heard a non-diabetic person saying they’ve felt that…

Okay, I’ll post again when he gets lab results, unfortunately he didn’t have time before work today so it might be a while.

Yes and no.

For diabetics they define 55 mg/dl as a critical low. It’s not because horrible things happen at 55, it’s just about statistics. The statistics say that the more time diabetics spend below 55 mg/dl, the more likely we are to wind up in the hospital or morgue. It’s because our blood sugars are more volatile, meaning that 55 could keep plummeting until we stroke out or other beef things happen. Also, our bodies aren’t accustomed to being down there anymore so we show cognitive decline earlier than our non-diabetic counterparts.

If you’re not diabetic, the “normal” range is a lot lower than they consider acceptable for diabetics. Even blood sugars in the 50s are considered normal, unless they’re accompanied by other symptoms. Less than 40 is not normal… but it also may not be a problem. And just because Dexcom read urgently, doesn’t mean that’s where his blood sugar actually was. CGM data can’t always be trusted. It’s an awesome tool for us, but it’s not as accurate as you might think. It could be a false low. It could even be true and “accurate” by Dexcom’s standards, even if his blood sugar was completely non-diabetic “normal”. If you look at this chart from Dexcom you’ll see that they give 20 mg/dl wiggle room in both directions for the lower ranges. That means Dexcom could read “LOW” when he has a perfectly “normal” blood sugar of 59.

On the other hand, BGs in the 300s are never normal. The lows are easier to brush off, but the highs justify testing. I’m guessing that’s all the doctor meant. They can’t just order every test under the sun. Insurance won’t cover the expense without valid medical reason. The highs are valid reasons, whereas the lows could be disputed.

Thanks, that’s helpful information, and I’m sure you’re right about the dr’s decision-making.

I found a study that looked at CGM results over 10 days for people who were not diabetic or pre-diabetic, not obese and no first-degree relatives with Type 1. They did get some lows, but most of them were determined to be CGM malfunctions. On the other hand, no one in his age group ever had readings above 160, and they spent 96% of the time in the 70-140 range. So more evidence that it’s the highs that are clinically significant. Here’s the study: Continuous Glucose Monitoring Profiles in Healthy Nondiabetic Participants: A Multicenter Prospective Study - PMC

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I agree with what @Robyn_H said although I would have used a different table.
From page 136 of the G7 user guide part of Table 3-C Concurrence of G7 sensor readings and YSI values by YSI glucose range (adults, n=308)

YSI is the FDA gold standard lab test for blood glucose testing. So as the YSI test results approach 40mg/dL the G7 results approach, but do not reach, coin toss accuracy. The G6 is similar in case that is what your son used.

I see you agree with what Robyn said, I just wanted to provide support for your agreement.

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The best way to prove a low is with a manual blood sugar stick. Its old fashioned and Docs trust it.

You can get noisy data outta the CGM. For example, lots of us get 'compression lows," which are false lows that occur while sleeping on the sensor. The sensor will read less accurately the lower your BG is. Manual is best for proving lows.

Unfortunately, the best way to imagine this scenario is that he is like a lawyer trying to prove a case to the Doctor in court. You want GOOD evidence that they can’t just blow off.

Yes, totally agree with @spdif and @Robyn_H that CGM lows are suspect. It’s just ironic because that’s why he decided to put on the CGM in the first place…he would feel shaky and sick if he went too long between meals. The high bg readings were a big surprise, he’s never had any diabetes symptoms like thirst etc.

Is he a diagnosed hypoglycemic?

No, not diagnosed hypoglycemic. This is really the beginning of whatever blood sugar journey this turns out to be. He put on the CGM due to hypoglycemia symptoms to see if in fact his blood sugar was actually getting low. And, yes, when he felt the symptoms he’d been having, the CGM read under 70. Happened multiple times in the week he wore it. He also calibrated with a glucose meter while low (not the under 40s tho) and it read the same.

The primary care doc he saw last week wasn’t concerned about the low readings he got on the CGM, said that happens to non-diabetics. She was however worried about the highs (went over 300 a couple times and lots of time in the 200s) and the fact that the predicted a1c was 6.3. She ordered a bunch of tests and I’m really hoping antibodies and c-peptide were among them, my son wasn’t sure and he hasn’t gotten them done yet.

Thanks for checking in.

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So, my son still hasn’t done the bloodwork. But I kind of can’t blame him because the doctor really didn’t order anything that looks at the blood sugar issue besides an a1c. She wants to rule out thyroid, anemia, and other metabolic issues due to my son telling her he feels run down. Fair enough, but no antibodies, no c-peptide, no OGTT, nothing that would give much information about the blood sugar issues that he came in for?Ugh.

She did request a metabolic panel which has a random (non-fasting) glucose in it. I suppose he could manipulate that by eating a high carb meal before the test which should give him an abnormal result to get her attention. Does that seem like a good strategy?

I honestly can’t believe that having readings in the 300s in the Dexcom Clarity app didn’t seem to have any impact on her approach…

Possibly this