Sudden, dramatic, night-time hypos unexplained

Hi all,
I hope someone can shed some light on a problem we're having. Out 11yo daughter (dx T1 17mth) has a Veo pump (Revel in US?) and Enlite CGMS for which we are very grateful. However, the CGM tells us that most nights she has very sudden, severe hypos followed by what we presume to be liver dumps resulting in his BGs come morning. Without the CGM we would most likely not be aware of these as she is hypo-unaware though the higher morning readings would suggest something is up at night.
She could be on a glucose level of 10mmol/l (180mg/dl) and within 10-15 minutes her CGM shows <2.2 mmol/l (38mg/dl) followed by an equally quick rise to perhaps 11mmol/l (198mg/dl) or more. We've tried everything we can think of.
We've given her a supper of full fat milk & occasionally some cheese, sometimes with very low bolus to cover. We've dropped her basal from 10pm until 3am by more than 60% of that leading up to 10pm. We've monitored exercise to see if it was being caused by PEL (post-exercise late onset hypo) but it happens even when she's had no exercise for days.
Usually it happens between 12:30 and perhaps 2am but more recently it's happened at 11:30 or 4:30. We've on occasion by luck 'caught' it by BG but the number we get is likely later than the actual event given the CGM is 10-15 behind so the BG shows something like 7.0. However, this continues to rise (Symogyi effect) as we prove with later BG tests.
From my reading I'm beginning to think it might be thyroid related though her last bloods were clear. She does have celiacs already. Any help much appreciated,



thanks for reply. Yes, we've given 200ml full fat milk as well as some cheese before bed, sometimes fully covered by insulin and other times with reduced insulin. However, she still drops rapidly seemingly regardless of how high she is.

As I say, we're out of ideas on this and worried,


Are you using a meter to confirm these numbers or is this SG. It's hard to believe her
BG is dropping 140 mg/dL in ten minutes while sleeping (no activity). You need to test
her with a meter every couple of hours for a few nights and get some good BG data.
Anytime her pump gives a low/high prediction you should do a meter test.

I have had many SG readings that drop 100 points in a few minutes but this happens
because the sensor is dieing. I also have sensors that fall out of calibration when
I'm not active, the Isig: just drops low or it flat-lines. This can also happen when
I stay in one position for a couple of hours.

You need to test, test, test....

I have no experience w/ the Enlite as we don't have it in primitive countries like the USA.

If she's trying protein/ fat and it's not covering the low, maybe something a bit more substantive? I've sort of had similar problems lately, we've had a bunch of really late dinners repeatedly so I have like 3U on board @ bedtime and I'm like "I don't want to go high but I don't want to go low and I'm SLEEPY!!" so I sort of fumble through it and have had a bunch of crappy results.

It might also be useful to try to eat dinner earlier, to "clear the decks" and get the stray "tail" of the dinner bolus out of the way before bedtime?


you're right to be cautious of CGM readings but the Enlite when properly calibrated is very accurate though naturally there's a 10-15min delay given that the reading is from the interstitial fluids. We have on occasion been 'lucky' enough to catch the low but it's typically already on the increase thanks to the counter-regulatory response of the liver. We do know from BG testing that the drop and rise does happen well within a 1 hour duration. Coupling that with the very reliable results of the CGM on 90% of occasions and the rep confirming that it was likely accurate, we're pretty confident (having rejected the possibility previously) that this is happening as described.

But your mention of the Isig: when I dug out the logs one evening I saw that the ISig did drop a lot as the 'low' began. I'm not sure of what the ISig reflects (signal strength or confidence?) but there is a correllation. Any other info would be useful.

Thanks to all responding - I'd really like to figure this out ahead of our endo appt. in 2 wks.

Also, she's on .5U/hr basal from 5pm to 10pm and then dropping to .3 until 3am - that's our latest effort to head off the events.

Thanks again,


Some things strike me as odd in your description of the events.

A fluctuation of 180 mg/dl to 38 mg/dl within 10 minutes is possible. However these are rare events with much insulin on board or result of a high metabolic rate. Like John I have my doubts about the accuracy of CGMS in general - especially in the short timeframe of 10 minutes. The way you describe it she experiences the drop even with little insulin on board. The question remains how the 142 mg/dl of blood glucose could disappear within 10 minutes. Celiacs can lead to a permanent inflammation of the intestine. In a severe and untreated case this can lead to the malabsorbtion of nutrient, amino acids and vitamins. Do you think the insulin is overtaking the absorbtion of the glucose in the first minutes? I doubt that insulin can act that fast with the passage through the skin but still it is one possibility to rule out. Have you tried different analog insulins like NovoLog, HumaLog or Apidra? Perhaps she is just showing some strange reaction to the insulin or the preservatives used. Even regular insulin can be worth a try - at least it can not cause quick lows. This may lead to much trial and error but it will be worth the effords.

The Symogyi effect is often mentioned but there is little scientific evidence about its existence. The biggest problem is that the Symogi effect is claimed to be a result of counter regulation. But counter regulation can only happen if there is no active insulin present. This is why most insulin dependent diabetics will not experience this effect at all. For us the counter regulation is broken because insulin is always present. In contrast some members have experienced the release of glucose due to emotional events like stress or falling in love. So there is some sort of hormonal and emotional component involved and according to the age of your daughter this might be something to consider too.


thanks for such an indepth answer. It's good to get others perspective on this. First off, nearly always when we 'see' this drop, she has no insulin - last bolus would typically be 5-6 hours previous. She's using Novorapid (Humalog?) only in her pump and we see a period of activity of about 4 hours.

Her nurse commented yesterday that .6U/hr basal from 6pm to 10pm might have a run-on effect through to 1am and she felt that level a bit high for her age. However, we established that a couple months ago along with other basal settings/carb ratios and felt it necessary then. Of course, we're gearing up now for another round of fasting basal testing - tricky with a 11yo!

I've read about hypothyroidism and adrenal suppression issues that can manifest with the hypos we have but I'm trying to identify the more common likely culprits first before 'taking on' another illness.

I'm pretty confident her celiac is well controlled. We'll ask for another test at next appt. but we try really hard to food and cook everything ourselves carefully. I even have a blog on our recipes! (

But (finally) I am convinced there is a hypo but you're right to be suspect about the rapid nature of it. However, we have proof (BG) that she is stable until we last check her around 12am and the CGM shows she would have been even to that point too and by then with very little insulin on board (apart from the basal). And we are sure that she comes in high in the morning consistent with the CGM reading then. So either the CGM is totally (and consistently) wrong and that perhaps she has too little basal to cover the dawn phenomenon (resulting in high morning readings) or she does go low early in the night and we're witnessing a liver dump effect come morning. Frankly, I'd prefer either of those scenarios to the sudden rapid drop that the CGM shows us!

Thanks again and your ideas most welcome,


I haven't ever done fasting basal testing to set rates. If I run low like 3 days in a row before a meal, sort of the scenario you are describing, although sometimes a late dinner, can linger on into the evening too, I'll lower the basal for the chunk of time in question. I have different rates for 1:00 AM-3:00 and then a higher one from 3:00 AM until 7:00 AM and that seems to have smoothed things out although they still change periodically?

I agree with Holger that the Symogyi effect which is often talked about is rare. However, the effect does happen when someone has a harsh low, even with some insulin on board (like a basal) you will counterregulate and that rebound high is the Symogyi effect.

I would also like emphasize Holgers last suggestion. There are conditions that can cause hypo problems. In particular adrenal issues can cause blood sugar regulation problems, and there are autoimmune conditions that may be involved. Your daughter should be tested for this. Also, if your daughter suffered high blood sugars she might have some kidney impairment. If your kidneys don't work properly, it can cause insulin to accumulate and cause hypos. There are also some medications that can cause hypos.

I'm sorry to hear you are still having problems. It sounds like the snack before bedtime did not work. Although you might think that a lack of specific exercise rules out PEL, your daughter may just be active enough during the day that it really doesn't matter.

It might be worth trying a more aggressive "meal" in the evening. I might suggest a "carb load." Perhaps 50 grams of fast acting carbs. Bolus enough to enable the uptake of the glucose, but not enough that you are nervous about insulin on board. Perhaps eat at 8pm and then most of the insulin will have worn off before you hit the time of concern. This may "prefeed" a low and avert it.

And finally, I would suggest that you are probably at the limits of how we can help you. I would enourage you to reach out wider. Read up on the literature on hypos in children, on PEL, etc. I can provide some pointers. And I think you can send some emails to medical experts and see if they have suggestions. I will msg you some contacts.

Hi jake42, I share your frustration as I've been experiencing similar drops at night myself. Of course, I'm a 51 year old female so not exactly the same situation, but in the last month I started dropping anywhere from 40 to 140 points between midnight and 3 a.m. then it would go back up. Sometimes it would be a shorter faster fall and recover but always between midnight and 3.

I know that this is happening and not just a fluke of the cgm because I went to bed high one night at 190 and woke up at 1:30 a.m. at 50 when my Dexcom alerted me. Confirmed it with a fingerstick.

My endo said that with these types of drops only at night typically what comes to mind is kidneys. My endo redid my labs to check kidney and liver function and ruled out problems there. I'm still waiting for thyroid results.

We have been gradually adjusting my basal down (I'm still on MDI so don't have the flexibility of the pump). I've been basal testing but making sure I start high enough to avert a low and then looking at starting and ending numbers each day along with my Dexcom graphs to see the trend and time.

I've been reading extensively and what I find echoes what Holger and Bsc said. Major stress (my husband was laid off), hormones (pre-menopause for me), medication (currently on antibiotic known to affect bg). I also read about adrenal issues but my endo didn't want to explore that option at this time, not sure why, maybe because it only happens during a 3 hour window.

Sounds very scary and you have no choice but to drastically reduce the basal and do frequent night time basal tests (hourly). It seems she has a sharp drop in her basals at a certain time at night (I have heard this referred to as a "valley"). You have to pinpoint the time period and reduce basals two or three hours before this happens. Sounds like it will be a very drastic reduction for a few hours. I would make sure there is no insulin active at bed time, no bolus for a late night snack. I would also raise her blood sugar target before bed. And definitely talk to your endo and seek medical advice, which I am sure you have done and are just asking for other ideas. Our DD has a 50 point drop no matter what most days from 2pm thru 4pm, then a sharp rise. I keep blood sugar higher during this time and do not correct during this time period. Keep observing, hourly testing. You can see the pattern; you just have to keep observing and charting. P.S. Do you think you can get the pump? Open to it? Because I am not sure how to addres this on MDI

the OP has a pump and a CGM, which is an ok substitute for nighttime basal tests. I'm not a big fan of basal tests as I've been able to work around them, particularly w/ the CGM. Diabetes is annoying enough without starving myself of sleep and food!


thanks for all the ideas (and @acidrock23). Thankfully, after a year of long fighting, we got a pump - and a CGM. She really needs it - impossible to predict anything without it. Her quality of life has improved dramatically since getting it and even though her A1C is about the same, it's good to see her get her life back. Now we're redoubling our efforts to find a way to bring that number down.

Her sugar variability and coeliacs makes it very difficult. We weigh everything that she eats, download her data every few days and spend hours looking for patterns. She takes her BG 10 times a day, we have different basal rates and carb ratios for different parts of the day. They might work for a week or two and then all wrong. Here TDD can be almost 30 for a few weeks and then drop to 22units/day. Exercise can affect her immediately, or a few hours after or 24 hours later - we sometimes think we have a pattern for certain exercise and then her sugars surprise us.

We have dropped her evening basal from .6 to .5 until 10pm. Then we've reduced it again from .375 to .3 until 3am. Then we dropped from .475 to .4 until 7am. We used to not give a bedtime snack, then (on advice) tried some proteins/fats (bolused and not) but it didn't seem to matter. It's early days on the lowered basal but last night she was more level all through the night with the exception of 4am when she dropped from 6.5mmol/l to 4.2 and back to 6.5 all within 30minutes. We'll see how it goes.

In Ireland, we only get 4-5month visits to the endo. We got our pump last Oct and haven't an appointment again until end Feb. The phone supports says to give snack before bed but that hasn't helped. At least we're not trying to do this on MDI...

Thanks again,



Our daughter, age 11, has recently suffered from 3 sudden night time hypos. On these 3 occasions she had to be admitted to hospital. However, the hospital are now at a loss to understand why her sugar level plummets so rapidly. At the hospital's request we had to ask our daughter, is she self administering insulin without our knowledge (we know she would not do that) but, as a precaution we now hide her insulin away. They even asked us if she makes herself sick after she eats, we refused to ask as she is a good weight and we know our daughter. On both these counts we know she is definitely not. We have even had to speak with a psychiatrist (to check us all out), we have gone with this because we know that we are good parents of four bright healthy children. This will not give us an answer why her sugar levels drop so suddenly, but will confirm that she would not self administer Insulin without our knowledge. She is on nova rapid 3 times a day with lantus glargine also injected once in the morning. Even overnight in the Hospital she could be 27 and drop to 14 or 22 to 12 and sometimes the whole night could be 14 ish.

Our daughter has been type 1 since 2004. Since she came out of hospital we are continuing to do regular night time blood tests. She usually goes to bed with a reading of 20.0 and on most occasions she still drops to 10.0 during the night. However, there are occasions when her level hardly drops at all during the night.

Our daughter is hypo unaware and we have looked into whether this could be thyroid related too. She has had a thyroid blood test that came back ok, but we think their is more going on with the thyroid and will be pushing for further tests. We are awaiting results for a metabolic test. We were advised that the hormonal side of things would make her sugar level high rather than low ?

All her insulin levels have been reduced, her carb to insulin ratio have been dropped and her sensitivity level have also been dropped.

Thank you for sharing your concerns and although our reply does not give any answers to the night time hypos, at least you know you are not alone.

Kind regards

Some members have reported rapid drops from Lantus. It is not supposed to act that way but for some it does happen. The Lantus does connect to fatty tissue and if this does not work there is some risk that the insulin will act quicker than expected. You can try to split the dosage of Lantus in two shots every 12 hours. This will allow better absorbtion in the tissue but I doubt that this will totally fix the problem. Another idea is to switch to Levemir. But if you do this then please try two shots of Levemir every 12 hours instead of one huge shot. These two shots will combine so you will have a good and even coverage for 24 hours. If you just take one shot of Levemir per day the risk is high that there will be a rapid drop comparable to what you experience with Lantus.

Holger, thanks for the advice. S is on a pump (finally) so we're just NovoRapid (humalog?) all the way. I did talk with the CGM people today and maybe have cleared up some issues. I'll post separately in reply to my own question for all to see. Thanks again, J

Just by way of followup to my own question, I spoke today with Medtronic about the CGM. It appears that the CGM can give very low readings whenever the sensor is not fully 'bathed' in the interstitial fluids - something that can happen if the sensor is inserted in the (very) low back and during sleep. We did much more regular checking of blood sugars over the last couple of nights and found that even though the CGM was alerting a low, the BG at that time showed much higher values.

Medtronic say the CGM is 20min late with the reading. By that I mean that the BG you take now won't show on the CGM for another 20 minutes. I find it more like 10-15min in practice.

So, I'm hoping that explains most of our lows, especially when I factor in that the low-glucose suspend (we use the VEO) would have contributed to later rises towards morning because of the absence of basal.

Hope this is of help to someone, and thanks for all the supportive advice,


Hello Jake. I don't have a diabetic child, but I was one, diagnosed at 16 back in the dark ages of diabetes care ('68). I wonder if your daughter might be growing into a woman. Because the hormone swings that come with this new territory can wreak havoc on basal rates. Is she menstruating yet or showing signs she will begin soon?

When I went on the pump I learned why MDI had never worked well for me - Because my basal rate varied so much in a 24 hour period as well as over the 4 week menstrual cycle.

My evening rate was highish -.550/hr. - through the supper hours; then dropping to .2 or .15 from 9pm-midnight; down further to .1 or even less, 12am-3am; then up to .4 from 3am-5:30am; .7, 5:30am-8am; and 1.0 8am-11-am; finally .4 from 11am-4:30pm.

In 24 hours my basal ranged ten fold, .1 to 1.0!

The other problem with some of us is that our basal rate as a whole rises or drops by x% during different parts of our cycle. After ovulation it climbs for 2 weeks then a steep drop as the period starts (down as much as 40% in my case) then slightly up and stable for two weeks prior to ovulation again.

This can be handled by creating multiple basal patterns for each part of the cycle. When 2 or 3 bad tests high or low happen she just switches to the next program.

I know both the beginning and end of menstruation is challenging for T1's as whatever pattern we are used to changes dramatically and often for awhile. If that IS what is happening to your daughter it is frustrating, exhausting and worrisome... but most likely normal. Just keep trying. It will settle out eventually!

Best luck!


Ok so you are giving her snacks before bed, but high fat doesn't seem to help. I think I saw you post that she is ceilic as well which - correct me if I'm wrong - means no wheat? So my suggestion is (because I have had this happen to me) is no insulin through the night and a bedtime snack of carbs - so rice crackers or cookies. They will keep her higher through the night than cheese.
Also when I was going through this very thing I ended up changing my evening long dose (i'm on needles) and that solved the problem of having lows at night and waking up at 16mmol. Once I removed the insulin at night I ended up having better readings in the morning. Also for some stupid reason they have you do Lantus at night (which for me was so dangerous) I changed it and took it in the morning instead and it made a world of difference. So perhaps when she is getting the doses could be altered to better care for the situation. Also I know the companies say it works for 24 hours - or that the rapid starts working in 20 min - but each body is different. I never listen to what the company claims because for me lantus only works for 16 hours and my novorapid still takes 2 hours to peak.
Good luck and I know you worry about your daughter but I was diagnosed at 5yrs old and I have travelled the world, done marathons, gone scuba diving and basically done anything I wanted because my parents always told me I could. They instilled in my the habit of checking my Blood sugars before sports and understanding that balance between activity and eating. She will have a totally normal life. Trust me she will be fine I've had it for 29 years now - no complications - and that's thanks to my parents.