What the Heck Is the Somogyi Swing?

By Dr . Joi Sutton|2018-08-15T15:45:52-04:00Updated: August 8th, 2018|Pet Care, Pet Diabetes, Pet Newsletter|13 Comments
  • Grey Cat and Pug Next to Each Other

Every now and then a diabetic pet just doesn’t seem to make sense. On paper it all seems so simple. You give insulin which should lower the pet’s blood glucose level for some period of time until it rises again. After all, insulin drives energy into cells. After an insulin injection we expect the blood glucose to go down, but sometimes it does not. Sometimes a pet doesn’t seem to respond to insulin at all. Sometimes, you get a Somogyi Swing.

When Pet Blood Glucose Numbers Don’t Make Sense

First, let’s talk about blood glucose curves. Human diabetics don’t run blood glucose curves on themselves. Human diabetics can dose themselves and know what they are going to eat, if they are going to eat, and how they react to various types of foods. They dose themselves appropriately for what they are about to ingest. Each day is a little different, and they adjust their insulin based on what they eat and when they eat.

Since animals can’t poke themselves with insulin, their human caretakers try to improve the pet’s diabetic control by having a consistent routine. Usually this means equally portioned meals and insulin doses every 12 hours. We figure that the pet will likely react the same way from one dose to another if we are feeding equally portioned meals. These meals are usually the same kind of food at each meal. This is the whole idea behind blood glucose curves. Again, humans don’t run curves on themselves because they are in control of what they eat and give themselves insulin injections accordingly.

How Do You Run a Blood Glucose Curve?

You first check the blood glucose right before a regularly scheduled insulin injection and meal. You then check the blood glucose every 2 hours until the next regularly scheduled insulin injection and meal. If the blood glucose goes lower than 150 mg/dl, we check it hourly until it starts to rise again.

A blood glucose curve tells us two things for pets:

  1. A curve tells us how low the blood glucose goes after a particular dose of insulin.
  2. A curve tells us how long a particular insulin lasts in a particular pet after a particular dose in that pet. Remember that each pet is unique in how it absorbs and metabolizes insulin. Some pets respond better to one insulin than another. It’s all very individual.

So, we expect that there will be a point a few hours after the insulin injection when the glucose hits the lowest point for that dose. We call that point where it “bottoms out” the “nadir”. We use the nadir to decide if we should increase the insulin dose, decrease the insulin dose, or leave the dose alone. We want the nadir to be somewhere around 100 mg/dl. What if that doesn’t happen? What if the glucose doesn’t drop at all? Sometimes it might even go up. That’s when we start to wonder if we might be experiencing the ‘Somogyi Swing’.

What is a ‘Somogyi Swing’?

The Somogyi Swing occurs if the dose of insulin is more than a pet needs. If the blood glucose dives down to hypoglycemia, the pet’s liver will likely react to save the day! The liver can turn stored glycogen into glucose. When the liver does this heroic gluconeogenesis, making glucose out of stored glycogen, we may then see a high blood glucose for hours or days thereafter. Truly, it can seem to make no sense whatsoever. Somogyi Swing can be a stinker to identify. Seriously, it is very very hard to recognize. We may wonder if the pet isn’t absorbing the insulin or if a pet isn’t responding to the insulin. We may wonder if the human is injecting the pet correctly. Or, we may consider dropping the insulin dose to see if we have a case of Somogyi Swing.

Of course, you should always chat with your veterinarian, who has examined your pet, before making dosing changes. If we suspect the Somogyi Swing, we back off on the insulin dosage and monitor over the next week and run a curve 5 to 7 days later.

Sometimes when folks first get the diagnosis of diabetes in their beloved pet they want to get the perfect dose as soon as possible! In their zeal to help Fluffy, they may increase the dosage of insulin too rapidly and bypass the actual appropriate dose for the pet. This Somogyi Swing phenomenon is why I advise folks to start slowly and sneak up on the dose. When I adjust the insulin dosage, I increase it by small increments. Whenever I change the insulin dosage I have the family run a blood glucose curve again in 5 to 7 days to see how that change has affected the glucose levels.

Have a question or comment? Then post below! I always enjoy hearing from my readers!

NOTE: Consult your veterinarian first to make sure my recommendations fit your pets special health needs.

About the Author: Dr . Joi Sutton

Dr. Joi Sutton is a 1993 graduate from Oregon State University. She has practiced both in emergency medicine and general practice. Dr. Sutton has done extensive international volunteer work though Veterinary Ventures, a nonprofit organization that takes teams of veterinarians to undeveloped countries for humane medical care. She also runs a small animal practice in South Florida. Connect with Dr. Joi on LinkedIn


  1. Sharon L Douglas October 10, 2021 at 1:10 pm - Reply

    My cat is over weight. He has been on Prozinc for a couple of years. He was doing pretty well but a month or so ago he has started to have big swings. 450 in the morning before shot then way down to 89 to 150 after 3 or 4 hours then back to the 400s at pm shot time.
    Is this the somogi effect?

  2. Anonymous June 15, 2020 at 6:21 pm - Reply

    I meant to also ask, it what level is a cat’s BG considered too low and needs intervention? My cat hit 78 Sunday (3 1/2hours after Prozinc), but it was back up to 108 2 1/2 hours later, and 138 2 hours after that.

    • Dr . Joi Sutton June 21, 2020 at 8:31 pm - Reply

      Your kitty may be going into remission. Chat with your veterinarian. 78 is 5e very low end of what would’ve co side red normal, but 3 hours after an insulin injection might land him in a hypoglycemic crisis. Do consult your veterinarian.

  3. Anonymous June 14, 2020 at 11:35 am - Reply

    Hi from Portland , OR. Miss you here.

    My 11 year old Birman was diagnosed with diabetes 5 weeks ago after taking prednisolone too long for his liver condition. You have addressed my questions somewhat in various articles, but am hoping to bring all the information together here.

    I understand the concept of several feedings a day to keep his glucose level. We started with 5 times a day, but have gone to 4 equal feedings- 7 am, 1 pm, 7 pm, then a bowl he nibbles on over night. He gets insulin (1 unit ProZinc) after the 7:00 feedings. (14 lb cat, should be 12- 13 lb)

    He is being fed Tiki Cat Succulent Chicken which is one of their zero carb foods. He gets a small piece of freeze dried salmon after a glucose test, otherwise no treats. Once or twice a week I get distracted and he gets a few bites of his sister’s NF food.

    I am having a hard time finding information on the science behind diabetes in cats. It bothers me to feed him the two meals that are not followed by insulin. I tell myself that since the food is zero carbs it shouldn’t really affect his BG.

    Is it true that cats don’t need carbs?

    Will you explain how cats digest their food and convert it to glucose? If he is getting zero carbs from his food, from where is the glucose coming? Why is it OK to feed the meals that aren’t followed by insulin.

    Do you recommend 4 equal feedings, or two larger meals with the insulin and 2 smaller meals the other times?

    Thanks to comments on one of your other articles, I am going to contact my vet regarding a chart as to adjusting his dose of insulin. There are times his am number is around 135, other times it is 175. A few days he was at 234. I think that may have been a symogyi swing. I have been adjusting a bit on my own (gets 3/4 unit if bg is 135) but will ask for Dr. recommended dosages.

    I am really hoping to get him in remission. His bloodwork 7 months prior had a glucose of 254 but no glucose in the urine. 5 weeks ago it was 400 with glucose so I think we caught it fairly early on.
    BTW, he was taken off the prednisolone. Continues to take Denamarin for his liver.

    Thank you for the assistance you are giving all of us that are fighting diabetes with our animals.

    • Dr . Joi Sutton June 21, 2020 at 8:42 pm - Reply

      Hello, Portland!

      Cats may prefer to nibble all day, but diabetic cats do best when they are given a meal twice daily—-at the time of the insulin injection. I don’t know who told you four meals per day, but I think 2 is best.

      Cats eat very little carbs in nature… mostly what their prey have in their stomachs. Cats are carnivores. This doesn’t mean they won’t eat carbs. Carbs do spike the blood glucose compared to protein and fat, so a low carb diet lends itself toward better glucose regulation. There is still energy in protein and fat.

      I’m glad your kitty is off the pred. It would be hard to achieve diabetic. remission while on steroids.

      You might read the AAHA 2018 Diabetes Guidelines. They are quite good and can be found on the internet for free.

      Best, Joi

  4. Jennifer McGreevy March 6, 2020 at 7:40 pm - Reply

    I think we’re experiencing the Somogyi affect, but the glucose levels are so high that I’m not sure what to do. My 25 pound terrier (normal weight was 31 pounds) started on 3ml of Vetsulin seven weeks ago. At first, my Vet increased the level gradually, with a .5ml increase every 5-7 days. I’ve sent glucose curves every week. Since his levels were still so high, including the lowest level during the day, she increased him from 6.5ml to 8ml two weeks ago and then from 8ml to 9ml a week ago. A day after the last increase, the levels were in the 100’s and 200’s for most of the day, peaking in the 500’s at the ends of the 12 hour period. After that one good day, however, my dog’s levels have increased dramatically and are now in the 300’s and 400’s during the day, with levels over 650 before his morning and evening shots. I’m scared at this point to back off of the insulin level, due to his glucose being so incredibly high. What would you recommend in this case? Thank you so much!

    • Dr . Joi Sutton March 6, 2020 at 8:55 pm - Reply

      I think you may be correct. Or, there could be insulin resistance. Or, your pet might just not respond well to the insulin chosen. Do chat with your vet about dropping the dose or changing insulin. Or, if you live in a large city there’s may be a vet internal medicine specialist who can help you. Most big cities have a specialty hospital with an internist. Or, you might also consider a different insulin for your pet. Be sure to eliminate e any causes of insulin resistance such as dental disease or a urinalysis infection or obesity.
      Also, just so we are talking the same language, we use the term units of insulin rather than ml. A unit is a much smaller amount than an ml (milliliter). Some insulins are u-40 meaning there are 40 units per milliliter. Other insulins are u-100, meaning there are 100 units of insulin per milliliter.

  5. riddhi March 20, 2019 at 10:12 am - Reply

    My cat is on Lantus 1.5 units twice a day for 20 days now. I have been giving him canned food exclusively for a month since he was diagnosed with diabetes.He is a 16 lbs cat. He gets 4 cans of 3oz food spaced out thru out the day. My vet suggested to not change his feeding routine or amount while he is on his insulin till we do the glucose curve. I have done two spot tests and seen slight diff in his bg ( he started with 450 and now is 398). My cat seems a bit more playful now. He was a lethargic, overweight cat with plantigrade gait.( we got him last year as foster)
    .I have been reading all your posts and my doctor has mentioned about the samogyi ( not the term but she did talk abt how body compensates for the low bg). Too anxious about doing the right thing
    My question is will the spaced out feeding routine affect the blood glucose curve?? I have been giving him high protein, low carb fancy feast classic but all different flavors. Should I stick to just one or two flavors only?
    How much should I wait after giving him his meal and insulin shot to do the random testing of glucose?
    the insulin shots I give by lifting the skin around the shoulders and front legs…sometimes i wonder if it even went thru his skin or not…though i can feel the needle piercing the skin. What are the external changes I can observe to see if my pet is getting better?

    thank you so much for your time!

    • Dr . Joi Sutton March 24, 2019 at 7:26 am - Reply

      Typically we will do a blood glucose curve 5 to 7 days after starting a pet on insulin. Or, run a curve 5 to 7 days after changing the ins7lin dose. I suggest you run a curve at home and share the results with your veterinarian to evaluate the dosage.
      I’m glad you are using low carb canned food. I don’t know how much variability there is between the flavors, soid likely stick with one flavor.
      Improved clinical signs would be less thirst and less voluminous urinations, feeling better, and looking better.
      Do strive for continued weight loss til you achieved proper body weight. Obesity is a huge factor in insulin resistance. If you get your kitty to proper body weight and continue the low carb canned food the hope is to get your cat into diabetic remission!

  6. Jeanne E. Barker September 1, 2018 at 3:54 am - Reply

    In order to curtail the symptoms of diabetic neuropathy and reduce the weakness in my dogs legs, I would appreciate knowing how much B-Complex and how often to inject it. My dog weighs 16.4 lbs. I have been giving her 2 units weekly and it doesn’t appear to be enough. Her weakness improves slightly but not enough to make a difference in her ability to jump up on the chair. Can you advise me, please? Thank you for your help. Cordially, Jeanne

    • Dr . Joi Sutton September 1, 2018 at 1:58 pm - Reply

      It would be inappropriate for me to advise dosing over the Internet, particulacy as your pet is not my patient. Please, chat with your veterinarian about this. 🙂

  7. Janey Phillips August 22, 2018 at 5:33 pm - Reply

    We were definitely guilty of this (going up too fast on our Westie’s insulin dose when he was first diagnosed). I’d like to comment on a couple of things that would have helped us if we’d known them during that initial phase. First, no one told us initially to stay with one dose for 5-7 days before making a change, while trying to regulate the dose of insulin. And, neither of our vets told us about the Somogyi swing early on. We were testing multiple times a day with our AlphaTrak2 and just did not understand what the curve should look like. We got up as high as 13.5 units on a dog that (admittedly a couple pounds lighter now) is now pretty stable in the 8-8.5 unit range on Novalin N twice a day. We continue to test our dog before each meal every day because he is still difficult to control, but we’ve tightened the loop and don’t think we could do much better. One other comment: sometimes it’s hard to know if a dose in relation to a relatively low blood glucose reading has caused a bounce to a high bg reading before the next meal, or if it somehow wasn’t enough. We have figured out that if it takes several days to get back to “normal”, it was probably a symogyi response followed by a degree of insulin resistance that takes a while to subside. If an insulin dose was too low (relative to the bg reading of the moment) then it seems to be much easier/quicker to get back where we want to be. Thanks, love your columns and I always learn something.

    • Dr . Joi Sutton August 25, 2018 at 1:58 pm - Reply

      Education is key! Great job.
      I’ve found that for animal care and our own health it is very important to be our own health advocates.
      🙂 Joi

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