The dawn phenomenon – why are blood sugars high in the morning?

Dawn phenomenon

Getting high blood sugars after a period of fasting is often puzzling to those not familiar with the Dawn Phenomenon. Why are blood sugars elevated if you haven’t eaten overnight?

This effect is also seen during fasting, even during prolonged fasting. There are two main effects – the Somogyi Effect and the Dawn Phenomenon.

Somogyi effect

The Somogyi effect is also called reactive hyperglycaemia and happens in type 2 diabetic patients on blood sugar lowering medications. The blood sugar sometimes drops in reaction to the night time dose of medication. This low blood sugar is dangerous, and in response, the body tries to raise it. Since the patient is asleep, he/she does not feel the hypoglycaemic symptoms of shakiness or tremors or confusion. By the time the patient awakens, the sugar is elevated without a good explanation. The high blood sugar occurs in reaction to the preceding low. This can be diagnosed by checking the blood sugar at 2am or 3am. If it is very low, then this is diagnostic of the Somogy Effect.

Dawn phenomenon

DawnPhenom2The Dawn Effect, sometimes also called the Dawn Phenomenon (DP) was first described about 30 years ago. It is estimated to occur in up to 75% of T2D patients although severity varies widely. It occurs both in those treated with insulin and those that are not. The circadian rhythm creates this DP.

Just before awakening (around 4am), the body secretes higher levels of growth hormone, cortisol, glucagon and adrenalin. Together, these are called the counter-regulatory hormones. That is, they counter the blood sugar lowering effects of insulin, meaning that they raise blood sugars. The nocturnal surge of growth hormone is considered the primary cause of the DP.

These normal circadian hormonal increases prepare our bodies for the day ahead. That is, glucagon tells the liver to start pushing out some glucose. Adrenalin gives our bodies some energy. Growth hormone is involved in repair and new synthesis of protein. Cortisol, the stress hormone increases as a general activator. After all, we are never quite so relaxed as deep sleep. So these hormones gently get us ready to wake up. A good ol’ fashioned hormonal kick in the pants, so to speak. Hormones are secreted in a pulsatile manner peaking in the early morning hours then falling to low levels during the day.

DawnPhenom1As these hormones all tend to raise blood sugars, we might expect that our sugars would go through the roof in the early morning. This does not actually happen.

Why? Insulin secretion also increases in the early morning to counteract the counter regulatory hormones. In other words, insulin is there to make sure blood sugars do not go too high. However, if you look closely at the blood sugar readings, there is a slight increase in the morning time.

So, in the normal, non-diabetic situation, blood sugars are not stable throughout 24 hours. The Dawn Effect happens in normal people. This is easily missed because the magnitude of the rise is usually very small – from 89 to 92 mg/dl. However, this effect was found in every patient studied. So, unless you are specifically looking for the DP, you are likely to miss it.

Think about it this way. Your body has the ability to store food energy as sugar (glycogen) and fat. When you eat, you store food energy. As you sleep (fasting), your body needs to release this stored energy. Around 4am or so, knowing that you will soon be waking up, your body prepares you for the upcoming day. It does this by increasing counter-regulatory hormones to release sugar into the blood. You can see that glucose production falls overnight and starts to ramp up around 4 am. In order to prevent the sugars from rising too much, insulin increases to act as a ‘brake’ on the system.

Type 2 diabetes

Balloon-deflated-300x165Now, what happens in the situation where you have T2D, or high insulin resistance? First, the technical explanation. Around 4 am, counter regulatory hormones surge and insulin is also released to counter this. However, in T2D, the body has high insulin resistance, meaning that the insulin has minimal effect at lowering the blood sugars. Since the counter regulatory hormones (mostly growth hormone) still are working, blood sugars rise unopposed, and therefore much higher than the normal non diabetic situation.

Balloon-inflated-300x202In the non diabetic (normal) situation, the liver is like a balloon. You eat, insulin goes up and food energy is stored as glycogen in the liver. As the balloon is deflated, the sugar goes in quite easily. As you fast, insulin falls and glycogen is turned back into energy to power the body.

Now, consider the situation of T2D. Over years of overconsumption, our liver is stuffed full of fat and sugar. As we eat, insulin goes up and tries to put more fat into a fatty liver. This is quite difficult. It’s like trying to inflate an overinflated balloon. The sugar and fat simply won’t go in anymore. That’s insulin resistance.

DoctorBut what happens when insulin starts to fall? You have a huge fatty liver that wants desperately to deflate itself (see last post). As soon insulin falls, sugar comes rushing out of the liver and into the blood. This results in the clinical diagnosis of T2D, when doctors are able to see the high blood sugars. So, what do they do? They prescribe more insulin.

This big whacking dose of injected insulin keeps the sugar bottled up inside the liver. This means that the blood sugar number looks better and looks like a job well done. But nothing is actually accomplished.

The underlying cause of insulin resistance is the fact that the liver is overstuffed with fat and sugar, like 10 pounds of sausage meat in a 5 pound skin. Nothing has been done to alleviate this situation.

So, patients must inject themselves day after day. Over time, they require higher and higher doses. A year later, the liver is like 15 pounds of sausage meat stuffed into a 5 pound skin.

The dawn phenomenon and type 2 diabetes

JeffIn the Dawn Phenomenon, the body is under orders to release some of the stored sugar into the bloodstream. Like the overinflated balloon, the liver puts forth prodigious amounts of sugar in order to relieve itself of this toxic sugar burden.

It’s like trying to hold a fart inside. As soon as we get to the bathroom, it’s ‘Fire in the Hole!’. When our liver gets the ‘go’ signal to release sugar, it does so in huge amounts, overwhelming the pitiful attempts of the insulin to keep it bottled up inside.

That’s the Dawn Phenomenon.


The same thing is seen during fasting. Remember, there are hormonal changes during fasting that include increases in growth hormone, adrenalin, glucagon and cortisol. These are exactly the same counter-regulatory hormones as seen in the DP. These are normal changes. As you fast, your insulin drops. Your body then tries to increase the glucose in the blood by encouraging the liver to release some of its stored sugar and fat. This is natural. However when you have T2D, there is too much sugar released from the liver which shows up in the blood like an uninvited guest.’This is a ‘placebo’ line. It serves no purpose but it makes us feel good.’

PlaceboIs this a bad thing? No, not at all. We are merely moving the sugar from the liver out into the blood. Lots of doctors consider it bad, because they are only concerned about the sugar that they see (in the blood). They do not concern themselves with the sugar that is hidden away.

After all, think about it this way. If you are not eating, where is the sugar coming from? It must come from inside your own body. There is no other alternative. You are simply moving the sugar from storage, out into the blood where you can see it. It is neither good nor bad.

Storing sugar in the liver

Insulin moves the sugar from the blood where they see it, and into the tissues (liver) where they cannot. It is no less bad, but they are able to pat themselves on the back for a job ‘well done’. it is not different from moving garbage from the kitchen underneath your bed. It smells the same, but you can’t see it.

I call drugs like these (insulin, sulfonlyureas) dracebos – placebos for doctors. They are medications that don’t actually help the patient in any way. The patient may still die of diabetic complications despite temporarily making the numbers look better and feeling like we accomplished something good. The history of medicine is the history of the placebo (and dracebo) effect.

Effects on blood sugar

In the IDM program, we typically use medications to keep blood sugars in a reasonable, but not low range during fasting. Insulin keeps all the sugar bottled up inside the body. If we stop insulin, there is a risk that it comes out much too quickly (like the overinflated ballon releasing all at once). So we want to use less insulin, but enough to release the stored sugars at a reasonable measured pace. A physician needs to adjust the medications to properly control the flow of sugar out of the liver.

The Dawn Phenomenon, or higher blood sugars during fasting does not mean you are doing anything wrong. It’s a normal occurrence. It just means that you have more work to do.

Some people have normal blood sugars except for the Dawn Phenomenon. This still indicates that there is too much sugar stuffed into their liver. They need to keep burning down that sugar. It means there is much more work to be done before they are cleared of their diabetes.

Think about it this way. The Dawn Phenomenon is simply moving sugar from body stores (liver) into the blood. That’s it. If your body stores are filled to bursting, then you will expel as much of that sugar as possible. By itself it is neither good nor bad. It is simply a marker that your body has too much sugar. Solution? Simple. Either don’t put any sugar in (LCHF) or burn it off (Fasting). Even better? LCHF + IF.

Learn more

Is your fasting blood glucose higher on low carb or keto? Five things to know

Try it

LCHF for beginners

Fasting for beginners (video course)

Top videos about diabetes

  • The essential problem with type 2 diabetes
  • Living low carb with Chris Hannaway
  • How to reverse type 2 diabetes

More >

More with Dr. Fung

Dr. Fung has his own blog at He is also active on Twitter.

His book The Obesity Code is available on Amazon.

The Obesity Code


  1. Paul
    Fantastic article... has helped me to understand more, just a shame there are still a lot of doctors who don't...
  2. robert

    "The failure of the Somogyi phenomenon to occur..."

    "The Somogyi Phenomenon - Sacred Cow or Bull?", Philip Raskin, MD, Arch Intern Med., 1984;144(4):781-787.


    "Session 17. The Somogyi Effect. Real or Myth? - Dr. Bernstein's Diabetes University"

  3. Regina Richards
    I've been doing 5-10 days fasts once a month along with LCHF since January. I'm feeling better and better and losing weight but I was also seeing this phenomenon and was worried by it. Thank you, Dr. Fung for explaining what this is and that it is my body doing exactly what it is supposed to do, healing.
  4. Ryan
    This is a great read and one of the biggest reasons I switched to a pump was to have more control over my basal to cover my pretty dynamic dawn phenomenon (I am type 1). I also have a diabetes site and some people may be interested in the list of items we have identified that can raise your blood sugar besides food (such as dawn phenomenon):

    Thanks for all of the great content!

  5. Toni
    Could this DP occur at other times of the day? I find that if my blood sugar gets close to 90 regardless of the time of day, my body starts making my blood sugar go up. Will my body eventually reset itself as I run out of sugar from the liver? Will my blood sugars eventually get lower than 90 if I keep at this low carb high fat lifestyle? I had an A1C done and it came one point into the pre-diabetic range. I refuse to be diabetic and suffer as I have seen my relatives suffer. It is a good wake up call for me.
  6. Adriane
    Aconteceu comigo e estava desesperada, até que li um artigo do Dr. Souto no Brazil que me esclareceu sobre esse efeito "amanhecer". É por isso que não devemos nos guitar pela insulina matinal em jejum.
  7. deborah conner
    This has been happening to me. I awaken about 4 sweating, alarmed and worried, "what am I doing wrong?" Does metformin help with this? Milk THistle? Alpha lipoic acid? I was on a very low intro dose of metformin bc I'd just begun measuring type 2 diabetic with an a1c of 6.6. I took it a month and stopped 6 weeks ago because I took the HFLC challenge and was feeling good, measuring ketones w urine strips, naturally falling into 19/8 fasting, 2 meals a day, no cravings.
  8. Ginny
    Thanks for the explanation, it's the clearest I've read for a layperson, most get too involved and I get lost, so again, thank you. What I fail to see in any of the info about DP is what can I do about it. Yes, LCHF and IF, I have been doing both for 3 months, not exceeding 20g Carbs per day and not exceeding the calories required for my goal BMR (which actually works out to be the same as my current BMR less 30%), more often it;s less as I don't feel hungry. I have no problem with IF, infact it comes quite naturally to me, but I have been experiencing some increases in my fingerprick numbers as the morning wears on, along with headache and nausea. In 3 months, I have lost 2kg. Yes, only 2kg. My A1c has dropped from 12.9 to 6.4 when checked a few weeks ago, so I am happy to see very positive results in regard to my health, but being obese with a need to lose more than 1/3 of my body weight, seeing some results there would be really nice about now! How do I achieve this with increasing blood sugars while fasting? If there is something else I can do when those numbers come up in the morning to bring them down (other than eating something), could someone please let me know? I am planning a trip to my doctor to ask for blood tests (hormones, thyroid and cortisol, all are issues I have had problems with in the past) and like to go in with a little bit of an idea of what I need to know/ask.
    Further info, I have been tried with Metformin, Gliclazide and Forxiga all with side effects that made them not an option, I seem to have this problem with many medications
    Any and all help would be appreciate xo
  9. ER
    I am a non-diabetic. I recently started taking 500mg metformin twice a day despite the fact that my blood sugar is normally in the 4.8- 5.2 mmol/L range. This morning my fasted glucose was 10.0 mmol/L. Is it a mistake to be taking the metformin? I started taking it because a number of endocrenologists are calling it a "longevity drug".
  10. Upset
    Sugar in the blood is bad because it forms advanced glycosylated end products which cause macrovascular and microvascular complications such as atherosclerosis, coronary artery disease, nephropatjy (kidney problems), retinopathy (eye problems), neuropathy (e.g decreased sensation especially in the fingers and toes).
    Sugar in the liver is stored as glycogen and does not cause these complications because it does not form advanced glycosylated end products. Thus, the purpose of metformin and other drugs is to help diabetics avoid these complications, although weight loss definitely plays a big part as well. Furthermore, not all diabetic drugs cause weight gain. Metformin certainly does not - it even causes weight loss in some.
    Please do your research before spreading misinformation that may cause harm and complications to thousands of diabetics out there.
    Reply: #12
  11. Jayapriya
    Doctor I've started this LCHF diet for about one week and along with my medication. One night I forgot to take my medication and next morning I saw my sugar level as 124 and was very worried because my sugar levels were normal before this incident. So I stared browsing for an explanation. I came across your article and soon understood what had happened. Now I know that there is no side effects due to my diet. I thank you from bottom of my heart and liver.
  12. AO
    Thank you! This article has great information but calling antihyperglycemics "medications that don't help the patient in any way" is quite the stretch.
  13. Karla
    In this sentence, it should say "store" not "stop": If we stop insulin, there is a risk that it comes out much too quickly.
  14. Elaine Lynn
    I wonder if this explains why my triglycerides were higher than normal after a 4 day water only fast? I thought TG's invariably decreased as a result of a fast. But if growth hormones, catecholamines etc. rose as a result, and my labs were drawn at 0600, maybe there was some element of DP involvement... Hmmm. Food for thought.
  15. Robert E.
    I am grateful for this article.
    I started LCHF on 9/1/17. As of today I have lost 35.5 lbs, I went from 38 units of Lantus a day to 35,30,25,20,18,15,12,10,8,5 and now 0 ( my Endocrinologist) told me to stop Lantus. Ohhh I forgot- I no longer take Farxiga, Janumet, And Bydureon.
    I'm still on Metforming 1,000 2/day.
    My glucose averages have been 82,85,87, for 14,30,60 days respectively and the reasons for Dr recommendations.
    After being a diabetic for 23 years, today I cannot explain nor justify with reasoning how nor why I did not know about LCHF before.
    Recently, after following Dr Fung's intermittent fasting 2-3 times a week (16:8), I stated to notice sugar readings over 100-142 in the morning for no reason. I typed my question on the search and this article came up. It makes absolute sense....
    Thank you, thank you, thank you.
    I'm feeling like a new person, my diabetes is getting better, and soon diabetes-reversed.
    Thank you all for your service to humanity.
    Atlanta, GA
  16. Total EMF Solutions
    Nice article but unfortunately high blood sugar is due to dirty electricity. Yes, I said it. Why? Due to empirical evidence it has shown to effect blood sugar every time. Power plants ramp up their dirty back up generators to handle demand at this time. I got the info from Sam Milham MD, MPH and have reproduced his findings for 6 years now with numerous people. Hope this helps.
    Reply: #24
  17. John Farrell
    I have started, what I believe is your program, Dr. Fung, but maybe I misunderstood. I am fasting, as much as 16 hours a day, most days. I find myself very comfortable in limiting my intake of food, in that, I never feel hungry or suffer the effects of low blood sugar, like in the past. I do see my readings in the morning have really increased and that bothered me a great deal until I saw your reasoning. Perhaps, where I misunderstood, as I stopped taking metformin (1,000 mg) twice a day and Glipizide (10 mg) twice a day. I am only a week into this but is ignoring my Doctor prescribed meds every day a mistake?
  18. Kimbree
    Thank you this was helpful. I’ve been concerned that my glucose level is higher upon waking than it is later in the day, after breaking my fast (doing 16/8, sometimes 23/2).
  19. Jill
    I have two questions, 1. Does this mean that once your liver heals your glucose levels should go back down to normal? By healing I mean once one has been fat adapted for long enough to release all of the excess glucose (Which I suspect could be upwards of 3 years? As that is how long it takes the liver to regenerate) and 2. Does all this glucose in the blood interfere with the fat burning mechanism?
    Reply: #28
  20. James
    I am a pre-diabetic (so no meds or insulin yet) and just started the LCHF + IF routine. On my first morning after the initial fast day I was shocked to find my glucose levels skyrocketed to 180's (it's normally 120-140 in the mornings). Thanks to this site, I understand what is going on and plan to continue the routine, but am concerned that I'll be doing some damage to my body by letting my glucose levels stay elevated for so many hours each morning (it gradually drops to normal range by mid-afternoon). Is there something I can do temporarily to suppress or eat up the excess glucose released by my liver? I can probably do some aerobic exercising to help drop it some as soon as I wake up but are there some natural supplements I can take before bedtime to control the rise until my liver is emptied of all the stored sugars?
  21. Kenny
    Hi James,

    I'm an healthy individual and I experienced the same dawn effect like what you said. As for me, in order to bring it down, I will do an hour low intensity exercise such as slow jog or cycle to counter the effect.

    As for me, it helps a lot.


  22. Name
    Best explanation on the Dawn phenomenon I've encountered so far, thanks a lot.
  23. Janet
    Thoroughly enjoyed book and all the videos. my only issue if after saying doctors lower blood sugar by insulin but don't really know how to treat the underlying cause, yet he says get your doctor to advise you on fasting, bs levels etc. how is that suppose to work
  24. Bob Johnson
    Simple commonality, not causality.

    It’s like saying everyone in the 1970’s that had cancer in that decade got it because phones cause cancer. This was proven because over 90% of those with cancer had telephones in their homes.

    Keto Vitae!

  25. juan carlos
    Hello, excellent explanation.
    My question is whether this phenomenon can also happen when doing a physical activity, such as running. I have verified that my blood sugar increases post-exercise.
    Should I expect an improvement over time?

    Thank you so much

  26. Michelle
    This is the best explanation I have ever read about Dawn Phenomenon! I have also always wondered WHY my blood glucose goes UP when I fast?? Now I totally understand. Thanks so much!
  27. Els
    This is such a helpful article. I’ve been wondering about the DF for quite a while and was worried about it. No more, thank you doc!
  28. Rita
  29. Claire
    I would like to make a question regarding high blood sugar while IF...So i've started 18:6 5 days now so i'm checking my blood sugar in the morning and after meals (i'm not diabetic) ,i was at 130 kg a while ago now i'm at 92.
    So blood sugar is in the morning at around 92-95 and after meals is the same most of the my question is ,is it possible IF stresses the body so much that raises glucose at that level 90s and so it has to stop from doing IF because it is bad for my body?
    All these come from a discussion i had in a keto group ,and they say if someone has 90 constantly to stop from doing IF because it's bad...what is your opinion about it?
    Thank you
    Reply: #30
  30. Kristin Parker Team Diet Doctor
    Claire, Yes, for some people, the stress of IF can raise cortisol which can raise blood sugar. The only way to know for sure if that's the case for you is to drop the fasting for a week or two and compare your readings.
  31. trish
    I am nondiabetic and have been on keto for 2 yrs. Stable normal weight. Using ketone blood meter also for glucose. In stable ketosis. Blood sugar with normal LCHF is generally in 80-90 range. When I do a 2-3 day fast, BS drops to 70-ish. Borderline. Normal? One day it hit 69. Anything to be concerned about? Should i stop fasting if it falls below 70? I was not experiencing any symptoms other than a bit of fatigue and hunger setting in.
    Reply: #32
  32. Kristin Parker Team Diet Doctor

    I am nondiabetic and have been on keto for 2 yrs. Stable normal weight. Using ketone blood meter also for glucose. In stable ketosis. Blood sugar with normal LCHF is generally in 80-90 range. When I do a 2-3 day fast, BS drops to 70-ish. Borderline. Normal? One day it hit 69. Anything to be concerned about? Should i stop fasting if it falls below 70? I was not experiencing any symptoms other than a bit of fatigue and hunger setting in.

    Here is some general advice that Dr Fung has posted in the past. If you are concerned or on medication please check with your doctor.
    "Listen to your body. If you feel unwell, then stop. Otherwise, if you are worried, reduce the fasting duration.

  33. Dr Kamal Bhardwaj
    First of all a big thanks to Dr Jason Fang. You have been the person i've been unknowingly lasting for since i have learned about raised sugar issues with me. Being an MBBS MD myself (39 years age) from India, i knew all the facts associated with diabetes and my raising of my blood sugar levels since many years relentlessly. But as it goes we are not very much self disciplined regarding our dietary choices and habits. Lots of years had passed by in this manner where i was trying all sorts of exercises to cut off my sugar numbers especially the dawn phenomenon ones but wasn't doing anything concrete on my diet restriction part. but last year as it happened, in April 2018 my low back pain which was remaining since years, started going worse and getting turned into sciatica. Having had all the scans normal, i decided to finally shed off some weight which had crossed 80 kgs (167 cms height) ie 28.7 BMI. Then changes also were evident. By september 2018 i had lost 8 kgs but my bolld sugars were 350 avg with an HbA1c of 14. i had actually developed blurred vision. then i started running and aerobics again with continous strict carb restricted and intermittent fasting plans. To my utter happiness, my vision came normal in a month, my HbA1c was 5.8 in April 2019 on NO DRUGS EVER, AT ALL . Means i am becoming NON DIABETIC from a state of DIABETES WITH INITIAL COMPLICATIONS. I have never taken any medication whatsoever for my diabetes. Its in fact a miracle regimen advocated by you Dr Fang. I have now learned to live in dietary discipline and all my lipid and sugar reports are absolutely normal and reaching new super normal goals. You are a living GOD to me sir.
  34. ET
    I am 48 years old, Asian, 171 cm. I have been limiting carb for a while but not the calories. My blood pressure was too high (100/140). I started taking high blood pressure medicine on 2019/01/12. Here are my numbers (different hospital):
    2019/05/16, 71.5kg, Cholestrol 199, Triglyceride 332, HDL 35, LDL 95, Hba1C 52, creatinine (blood) 1.
    2019/09/23, 71.5kg, Cholestrol 211, Triglyceride 127, HDL 49, LDL 165, creatinine (blood) 1.2.
    I have a stage 2 CKD:-( Most likely I am insulin resistant:-(
    I started LC+IMF/TRF(16:8) on 2019/09/24. After 2 weeks (69kg), my doctor halved my blood pressure medicine because it went down to 63/110. I started IMF/TRF(20:2) on 2019/10/26. I am now 65.7kg. My morning fasting blood glucose has been 96-110. If the higher blood glucose level is due to the Dawn Phenomenon (hopefully), how long will this last? How can I tell if my insulin resistant level has improved without going to a hospital? Can measuring blood glucose 2 hours after a meal be a OK indicator for that?
  35. Arif Amir
    DietDoctor has changed my life. I started my keto journey in 2016. My weight was around 120Kgs and I was using medications for high bloodpressure. In 7 months, I managed to reduce my weight to 90kgs.

Leave a reply

Reply to comment #0 by

Older posts