Good evening - I'm Dr. Sara. I'm a licensed veterinarian who works exclusively with dogs and cats. I'm so sorry that you've been having such a rough go with Greta's diabetes! It took me a few moments to read through your detailed history - thank you so much for that. I do have to say, though, that to be still managing her diabetes after this many years is quite good. We don't always get more than a year or two with our diabetic pets, so she is a bit ahead of the curve here.
Firstly, even though the human pharmacists treat them as if they are equal, Novolin and Humulin absolutely do not work similarly in dogs. It's my understanding that in humans they work very similarly, but in veterinary medicine we frequently see that you cannot switch from one to the other without causing issues. I've had dogs regulated quite well on each insulin - sometimes my clients do need to use the Novolin because it's significantly cheaper. I just don't switch dogs back and forth without some conversation and some blood sugar checks. Our WalMarts where I live all carry Novolin and actually push it on my clients - suggesting it as a cheaper alternative to Humulin when I prescribe it, so I'm surprised to hear that your WalMart isn't carrying it.
Having said that, neither Novolin or Humulin are regarded as fantastically effective insulin choices for diabetic dogs, as they often don't have the right duration of action. So I'm glad to see that you're no longer using this. I did have good experiences with Vetsulin but I stopped using it some time ago when it went though a recall and period of time where it was not available for us to purchase. We had to switch all of my patients off of it, which was extremely frustrating for us and for our clients, so I'm not a big fan of the veterinary insulins anymore for fear that they could potentially have shortage or backorder problems again in the future. I trust the supply of human insulins a bit more.
Before we talk about insulin choice, we need to discuss some other things that could be going on that could interfere with her response to insulin. All diabetic dogs should have regular urine cultures and full blood panels (CBC, chemistry, heartworm and tick screening test), and physical exams focusing on any skin or dental infections that might be present. We are also looking for other diseases like cushing's syndrome, kidney issues, or evidence of infection or inflammation. Inflammatory or infectious conditions like skin infections or bladder infections can interfere with the effectiveness of the insulin, so if I'm having trouble managing a patient, I typically recommend the blood and urine tests. Diabetic pets are very prone to urinary tract infections, and they don't always show up on a typical in house urinalysis - they need to have urine sent to the lab to incubate and see if it grows anything. Many specialists will also do an abdominal ultrasound and/or some chest X-rays as a survey to look for other non-diabetic diseases, specifically masses or cancers. Any illness aside from the diabetes can interfere with the insulin's effectiveness.
Another thing to consider would be a switch to a prescription diabetic diet like Royal Canin Diabetic or Purina DCO. These can make the world of difference in maintaining a low insulin requirement because they are formulated specifically for diabetic pets and held to very high quality control standards. I've seen pets decrease their insulin requirements by 10-15 units after switching to one of these diets. Also, I suggest a high quality probiotic like Purina's FortiFlora to support overall GI tract health and digestion.
On to insulins - Both glargine (lantus) and detemir (levemir) are the new "darling" insulins in veterinary medicine. I say that tongue in cheek a bit because the favored insulins among the profession do seem to shift about every 5 years or so. In any case, if you are seeing a Somogyi effect where the sugar drops too low at any point in the day then rebounds quite high, it means that the dose of insulin is too high and we need to decrease it. Once we are no longer seeing her drop too low, then we can evaluate the duration of action. As long as she is going too low at some point in the day, she is going to rebound high, so the goal would be to decrease the insulin until we are no longer dipping below about 60-70 at our lowest point. At that point, if it seems that the vetsulin duration isn't long enough, I'd probably be heading toward the glargine (lantus) because it has a much longer duration of action. Unfortunately, lantus is quite expensive, however so is a trip to the specialist ;)
It's likely at this point that your vet is pitching the idea of referral because he can sense that you're becoming frustrated. I've been in that situation too as a vet - I can tell that the owners aren't happy with their results, so I try to send them "up the chain" so that they can hopefully get results faster. It may also be that your vet will need to step out of their normal comfort zone to deal with Greta's problems. Most of the time your vet knows academically what to do, but may be holding back on the recommendations for further expensive testing for fear that you'll become more frustrated by their suggestion that you spend more money. I'm always happy to enter unfamiliar territory with my clients as long as they're understanding of the fact that I'm treading on new ground for myself, but I'm doing it with all the support I can muster from my texts and consultations with peers and sometimes even with specialists. I do, however, always recommend that if a client is going to seek a second opinion, that they go "vertical" not "horizontal" - meaning that they move up to a specialty hospital rather than move laterally to another general practitioner who is likely just as far out of his comfort zone dealing with your pet than your current vet.
Please let me know what other questions I can handle for you :)
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