Ask Dr. Jason Fung

Ask Dr. Jason Fung

I’m a big fan of Dr. Jason Fung, the Canadian nephrologist. He’s a world-leading expert on intermittent fasting and LCHF, especially for treating people with type 2 diabetes.

Dr. Fung has agreed to answer questions weekly on our membership site (free trial one month). Members can also read questions and answers from other people:

Jason FungAsk Dr. Jason Fung (for members)


For more about Dr. Fung visit his website

You can also check out our popular video interview with him, about the perfect treatment for diabetes and weight loss.

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  1. Jude
    Hi Dr. Fung

    I would like to communicate with you about IF/Fasting in general for HIV+ people interested in fasting to renew new cells?

    Please advise asap

    Thanks in advance

    From Partner of HIV+ wife

    I look forward to your speedy response

    Yours respectingly

    Fasting Student

    Reply: #52
  2. Peter Biörck Team Diet Doctor
    Hi Jude!

    Members can ask Dr Fung shorter general questions here:

    If you would like to come in contact with Dr Fung then I would try this page:

  3. sampath
    I started alternate day fasting a month ago and i went down from 205 to 188 as of today. my bloodpressure has become normal, my heart pulse rate has come down to 60. I thank Dr. jason fung for educating everyone on fasting.
  4. Charles
    I am 20 years into being a Type 2 diabetic and 8 months ago diagnosed with MG; I am too weak to exercise plus have constant low back pain from a failed back surgery. I use a mobility scooter and wear a patch over the eye that will not lift or focus because of the MG. I thought I was on a lot of meds for diabetes, cholesterol and heart failure, now I am really on a lot of meds! I have been taking cbd cream for my back pain, and it works so well and I heard that it can help with diabetes, I signed up to rep a company that has the oil (with no THC). Do you know if this would help?
  5. Anna Sabath
    I am a big fan of all your books I’ve read the obesity code I got diagnosed with early stages of diabetes i’m a big fan of fasting I did a 10 day fast and the same day of the last 10 days I had a blood work done and I was still prediabetic I also did a 4 Day Dr. fast no water no food my blood sugar goes from 87 to 106 that’s with dinner to dinner fasting since January 4 of this year I’m struggling with trying to lose weight I can’t seem to get the weight off even though I do dinner to dinner my meals are under 600 cal and I’m still not losing weight
  6. jeff howell
    do I KEEP taking insulin while taking dr. fungs regimen ?
  7. Bruce Witte
    Dr Fung I have been following your teachings since last April. I started at 440 lbs and today weighed in at 254. Amazing results from LCHF dieting and have been doing 16:8,18:6, & 20:4 since Jan this year. I have psoriatic arthritis and had bilateral hip replacements,the right shoulder and need the othe replaced. Thanks to Keto I went back to work PRN as a paramedic. I’m 60 and have been obese my entire life. A carb addict. This truly shuts off the binge mode switch!! Thank you for sharing this with the world!!!
  8. 1 comment removed
  9. Dean
    I am a 66 y/o "pre diabetic" with controlled HPT. I have been following dietary sites now for a couple years starting with Dr. William Davis. Wheat free was amazing for my health. I have done an almost strict LCHF diet for a year starting out with the Keto diet and now intermittant fasting. Since the peak I have lost about 30 lbs and have good blood work (now) with the exception of fasting insulin at 10 and the same stick blood sugar 119 (USA) Since I am a Sonographer I have looked at my heart, blood vessels and liver over the years as part of my job. I have not had any alcohol in over 30 years. Still, I have had a fatty liver (ultrasound) for years following carefully the recommended dietary guidelines. Was very athletic for years until blew out a knee and several discs. (pretty severe sciatica for years so limited exercise since) However fatty liver has remained although liver tests have improved. My issue is "dawn phenomena" even after days of fasting. At the moment I am into my 5th day of water fast (have done 4, many 2 and 3 day, and usually fast 20 eat 4) and still my blood sugar goes up. When I eat, my sugars are say 105 to 115. When I fast they shoot up and stay up all day/night in the 125 to 140 range. Right now in 5th day I just stuck a 121. (frustrating.) From what I read I have likely have a severely insulin resistant liver and likely other places. Doing the calc on 10 insulin 119 glucose (from last official lab) I am in the severely resistant category. I have started some high intensity training on a stationary recumbent bike which is supposed to make muscles more glucose storage ability. Since I have a medical background and have read about everything I can get my hands on and watched Dr. Fung plus MANY others on you tube (awesome resource). Since I also am involved in engineering I appreciate Ivor Cummins approach a lot. BUT....I am getting discouraged. Help me understand how my blood glucose can stay so high on a water fast of this length considering I am likely only 50 grams a day carbs on average and have reduced protein when I feed as well. Do I just have to run this dang liver out of all stores??? Any encouragement you can give me on when to expect this blasted organ to give up???
  10. Hklm
    I'm very excited about the videos and books for Jason Fung.
    As I been fasting many years before for religious purposes, but it was always getting me a relief and making me a healthy during fasting Period.
    My Question: As I heard and told by some, that fasting Affects Kidney, and as Jason Fung is a nephrologist, Is that any indication for, is there any effects of fasting on that organ? I didn't have any problem for my life during my fasting. Please Advise!


  11. Robert
    I heard Dr Fung's name just now. Wonder if fasting method can be used to control psoriasis. Thanks
  12. Tza
    I fasted for only about 70 hours when my vision started getting weird after i went did some cardio at the gym. So i ate something bcus it really scared me, i thought thats what i needed to do. Shortly after i ate, my right hand and right side area of my nose and underneath that one side of my nose started going numb also. I was having a hard time reading words and Reading has always been a favorite pastime of mine. It was my first time fasting for that long. I was excited to shed fat but i didnt lose any weight at all. Please, why did that happen?
  13. Cheryl S.
    Dear Dr. Fung,
    I am so desperate to lose weight - I am a type 2 diabetic on multiple medications including 3 types of insulin. I've tried the keto diet for a few months and had success bringing my blood glucose numbers down, but did not lose a single pound. I would like to try fasting, however I've had some blood sugar lows (70 or below) and am afraid fasting would make those worse. The advice from my endocrinologist was to take glucose tablets to counteract the blood sugar lows, which of course negates the keto effect and makes the whole idea behind the diet null. The doctor is reluctant to lower my insulin dosage, which I am convinced is contributing to my inability to lose weight. Obviously a low carb diet has some positive effects on my body, but is not impacting my weight. How can I approach the idea of intermittent fasting while combatting blood sugar lows while on insulin? Will the glucose tablets I have to take to bring my blood sugar back to normal negate the effects of the fast? Is fasting the only way to combat the insulin resistance I'm certain I am experiencing? Please - I have been fighting this issue for well over 20 years with no success. As you state in your book, I will lose as much as 25 pounds on a given diet, only to have the effectiveness wear off and gain it back plus 25 pounds more. I am now in my mid-40s, experiencing joint pain from the extra weight, battling the depression and fatigue that come with the ongoing struggle, I'm convinced I am over-medicated, and I get no satisfaction from my physicians. Your book spoke to me, but I am not sure I can implement the fasting due to my medications and blood sugar lows. Any advice would be greatly appreciated! Thank you!!
    Reply: #68
  14. Jamal
    Hello! I have some questions regarding my health and recent fasts. In late December 2018, my appendix ruptured and I was rushed into surgery. They removed my appendix, nearly 6 ft of my large intestine and a foot of my colon and left a massive scar going down my belly. I gained a bunch of weight since then. It is now August and last month I gave water fasting a shot. I made it 10 days and I experienced some brutal symptoms. It was 3 am and I felt some pressure in my lower back near my kidneys. I got up and went and went to use the restroom. I was very dizzy. I could hardly maintain my balance. So I sat down on the edge of my bathtub and I passed out. It was only a few seconds I believe. I was able to get up, I was scared and thought something was wrong and decided to go and break my fast. On my way to the kitchen, my hearing and vision started to fade rapidly. I wasn't prepared to break my fast. All I had was plums so I broke it with that. I instantly felt better but my kidney area bothered me for the next couple weeks. I feel better now. I really want to continue water fasting but I was hoping you could tell me what went wrong. Also, I was drinking distilled water. I don't know if that may have played a role or not.
  15. Sara
    I had a question. What about low blood sugar levels. I ask my mother to fast or eat less, and she did fasting (our ramadan) and she had to stop as she stopped feeling her toes. This idea is great that fasting can cure you, but my mother must have two meals a day with metmorfin (two metmorfin pills per meal). I want her to come off of that. I'm scared that if she doesn't eat all day, she won't feel her toes again (tingling sensation followed by numbness over time). I remember she used to be only on one pill per meal, now it has increased to two.
    I wish Mr. Fung could address this in a youtube video. Or maybe he has? Can anyone give me the link if he has addressed this issue.

    Thank you.

  16. David Tran
    Is this the same dr. Fung who helped George st. Pierre with his ulcerative colitis ?

    Dave ,

  17. Vegas Jen

    I'm desperate for help. I have been trying to lose weight for 7 years now. Tried HIT training 5 days a week, personal trainers, low fat, low carb no matter what I do I cannot drop my weight below 170 and I'm only 5 feet. I've been doing IF for a little over 1 month now with 0 results. I am doing 24 hour fasts. I don't eat bad during my eating window, I reach for whole unprocessed foods, salad and have been staying away from carbs. I will say that my sugar cravings are unbearable ! Any advice would be truly helpful.....

    Desperate in Vegas

    Reply: #69
  18. russell
    It sounds like you need to find a different doctor! You need a doctor who will support your dietary changes, not insist on continuing to medicate you! I do not have diabetes, and I'm NOT a doctor, but pretty much everything I've seen on the topic is that once starting a keto diet, most diabetics are able to significantly reduce or stop medications--with the advice/help from their doctor. I sounds like your doctor is not helping you. Please take care of YOU and get yourself a doctor who knows/understands/advises LCHF.
  19. russell
    Hi Jen,
    Hard to say what's going on, other than it sounds like you are starving yourself for nutrition. Your body NEEDS some good solid whole food to function. Intermittent fasting is something you should try if you were losing weight but then hit a plateau and stalled. To me, your story sounds like you've been pushing yourself entirely too hard for years and have been very unforgiving of yourself...and now you're being stingy with the nourishment your body needs! Time to try something different!

    Go back to the basics. Do the 2-week challenge or pick a meal plan and follow it so you're getting adequate nourishment. If your body feels like it's being starved, it's going to hold onto every ounce of fat it's got! Once your body learns that it's going to get everything it needs in 2 or 3 meals every day, it's going to "relax" and start releasing those fat stores for energy. If you still feel like intermittent fasting is the only way, then go for a 16:8 plan, where you fast for 16 hours (say, from 6pm until 10am the next day), and then eat 2 or 3 low-carb, high-fat, adequate protein meals in an 8-hour window. Just make sure you are eating enough!!! Don't restrict calories. Don't be afraid of fat. If you give yourself the nutrition your body needs, the cravings will disappear.

  20. Ranjan Gunawardena
    Hi Dr Jason,
    Have you published a book on treatment for Diabetes, if so could you please email details how to puchase it.
  21. Matthew Combe
    Dear Dr Jason Fung, I have your three books and I've been following your strategies for about 12 months. I've had some success in the right direction using your strategies. Today I told a friend about your suggestions and he said use Google Scholar to try and find peer reviews papers that Dr Jason Fung has put up 4 review... to save me the time Jason could you please direct me to those reviews that you no doubt have put up that prove your strategies are on the right path many thanks Matt
  22. shawn
    Dear Dr Fung. Greatings. Here is my history of type 2.
    2003 went to a new Doctor for initial check up.
    She took my sugar test. She said I am prediabetic with high cholesterol.
    She prescribed lipitor.
    Lipitor made me diabetic.
    Then she started to prescribe 8 medications from high blood pressure to victoza and other pills.
    I just don't get it. I was relatively a healthy guy in sports and then suddenly I a was a sick diabedic person. Each time I went for a check up and disclosed to her about side effects of medication she subscribed new medications. I ended up taking 12 medications a day! I asked her about side effects and being sicker. She replied positive exceeds negatives. I was paying a lot for medications and doctor. My quality of life never improved from the day I visited her.
    The after years of dickness income across your article. I started to fast by keeping my daily calory intales to around 1000. I stoped taking victoza. Within several months I started to lose weight. I lost 20 pounds with several months. From 253 to 233. My goal is the magic number of 200 pounds. I no longer see my doctor. I feel good. I realized that the medications were toxic and made me feel sick. They simply don't work.
  23. Liquan
    Hi Doc Jason,

    This is Liquan from New Zealand. I have been watching your youtube sessions on fasting.

    I have tried many two days and three days fasting but never made it to the fourth day. And I have noticed that every time the weight loss is less than the first fasting I did. And whenever I started to eat, I put a couple of Kg back immediately.

    I have done a meal after two days fast, then fasted for three days, then a meal, then I am planning to go for another week.

    Could you please:
    1. Explain why the weight loss is less dramatic to the initial fasting? Does it mean if I fast too often, eventually my body will get used to it and not losing any weight?
    2. Suggest what to eat to break your fast?

    Thank you so much for your time.


  24. Jonathan Khan
    Don't forget to workout spiritually.
    Tomorrow is not promised for any of us. Watch (Free 30 minute movie.) If you don't know the truth, you don't know who's lying.
  25. Mary
    Dr Fung, I have been incorporating IF into my Keto lifestyle program since October 2nd. I really have
    found little problems, in fact noticed less inflammation in joints. Goal is avoid T2D, Obesity, and stay healthy.
    I am 69. The concerns that have developed are increase in blood sugars (94-96 average prior/ now average 110-120) taken in a.m. P.m. blood sugars taken 4 hours post last meal are usually 110-107. Prior they were in the low 90s. Blood Ketones have remained with in range of Ketosis (1.2-3.1) The past couple of days when I increased IF to a 20:4 regime I am feeling tired, sleepy in early afternoon, hungry, and unease in my stomach. Are the blood sugar part of sugar resistance and will eventaully correct? Is the unease in the stomach caused by electrolyte or salt depletion? My Keto stats are as follows: began (07/17/18), Ketosis apparent since 07/20/18, lost 20 pounds, B/P gradually decreasing (from 146/92 to 128/82 ), exercise usually 300-400 calories/d , exercise 6 days a week, average carb intake since 1 Oct is 9-10 (no net carbs), Protein average - 72, Fat average - 120. Drink minimum 2000 ml/d. The change to a shorter eating window/longer fasting window seems more discomforting.
    Any advise?
  26. Alexander
    Dr Jason Fung, thank you very much. I am 60 years old 6 ft tall and I live in San Antonio, Texas. I am a diabetic and I have not taken meds in about 7 years. I have been able to control my sugars by my dietary habits but I have had to work at it and avoid many foods and that included fruits.

    I wanted to enjoy fruits but my sugars would always go up when I did eat them. I read some articles that you published here on the internet and I followed them. I did not consult my doctor because they are to eager to give me meds. By the way, I am a veteran and this is the VA hospital.

    I kept a glucometer and some chocolate truffles with me at all times. I head to abort 2 weeks into my first attempt since my sugars dropped to under 50 mg/ dL. I was not too concerned since I’ve been as low as 40 mg/dL. So I know what it feels like that low. I had made myself a promise that if it fell below 50 mg/dL that I would abort and I did. But then I did it again a week later and my sugars got as low as the upper 50’s mg/dL then began to rise up to the 70’s mg/dL. So I completed it in the second attempt.

    I fasted for 21 days and my sugars went down, I had an A1C Of 7.5 and it went down to a 5.0.
    I’ll also have you know that I met some extreme challenges. My family tried to talk me out of doing it and a friend that I was working with took me with him to restaurants and tried tempting me. But since I only eat organic food, I was well prepared to avoid temptation.

    I then splurged on fruits and ate more food than before including bread which I haven’t done in a long time. I gained most of the weight that I lost but I’m fasting again. I went from 225 to 169 lbs. I weighted 205 starting this fast and am completing day 4. My sugar was at 70 mg/dL this morning.

    My sugars were elevated again so I’m adjusting it again. I testing myself and my body and I think that I’ve got myself figured out and I’m ready to control myself without such strict rules but eating more sensible anymore.

    So, I too agree with you and others that it is very doable. I too am proof and have many witnesses. The biggest downside was that my face wrinkled up with my weight loss.

    Anyway again, thank you very much.

  27. Jason
    Would fasting help the body to lower Ferritin levels in someone with Hematomachrosis?
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