Hi Cheryl and welcome to our forum, but so sorry that Reagan is struggling. However.... so thankful that you already had the cTLI test done to see if EPI is what Reagan is struggling with.
If it is EPI, ask for the actual test results... this will better help us help you.
Also... did you have the B12 test done at the same time? if so, ask for those actual test result values to.
If EPI, the vet will want to put Reagan on the proper pancreatic enzymes... They should be porcine enzymes, powder is best. Make sure the Lipase enzyme level is around 71,400.... do not go with a product that has Lipase enzymes at 9,000 USP units... in which case it is cost negative since you will have to use a lot more ..... Typically vets will prescribe a prescription enzyme like Viokase, PancrePlus, etc (there are lots of brands) but many of us use ENzymeDiane 6x https://enzymediane.com/ because it is food grade generic and you can save a ton of money. Some folks start with a prescription brand and then switch over once that runs out to a food grade/generic brand. ... but this is totally up to you,
here is our list of enzymes: https://epi4dogs.com/enzyme-list/
FOr powdered enzymes, Start with 1 level tsp of powdered enzymes per 1 cup kibble, add enough water to moisten the food, mix and let sit for 20 minutes (to avoid possible mouth sores) and then serve. if serving wet food, reduce the amount of enzymes to 1/2 tsp to 3/4 tsp per 1 cup wet food (since there is already a lot of moisture in the food)
Next... if EPI, ALL dogs with EPI have SID (small intestinal dysbiosis)... which has most of the same symptoms as EPI.... so if after say 3 or 5 days, you are doing everything right with the enzymes, but the dog still has loose stools, then most likely the enzymes are indeed working, but what you are seeing is the results of SID.... in which case your can try a prebiotic... or try slippery elm (a mucilage with prebiotic properties)... if this doesn't stop the loose stools, then talk to your vet about trying a probiotic with prebiotics. SOme of the brands we suggest, but it really depends on the individual dog's gut flora what will be most effective.... anyway... so some of the brands that we suggest are: Proviable, or Visbiome, (from your vet) or (you can try OTC) Mercola COmplete PRobiotics or VetriScience Mega Probiotics. But please know to ALWAYS start with less than half the recommended dose and work your way up to a full dose over the course of a week or two. If this all fails to get SID under good control, then you will need to have a conversation with your vet about starting Reagan on a course of Tylan antibiotic... but try your best not to have to use an antibiotic if you can....... and do not let your vet prescribe Metronidazole (Flagyl) this is not good for dogs with chronic gastrointestinal dysbiosis. Our goal is to keep SID under good control... to-date we do not know how to eradicate SID.... but hopefully in the near future we will have a better handle on it!
Next you can talk to your vet about diet... or just manage diet on your own. EPI dogs usually do not do well on a prescription diet UNLESS there is another condition that needs to have a special diet (like a food sensitivity in which case we suggest trying a prescription hydrolysed food). We typically recommend "starting" with an over the counter diet that has less than 4% fiber content since fiber can inhibit the efficacy of the enzymes from anywhere between 0% to 50%.... and we have no idea which dog will be affected, if affected and by how much. also... start with a food that avoids splitting peas, lentils, legumes (using them more than once in varying forms) and avoid foods with peas, etc as one of the top 3 ingredients.... as this can encourage SID to get even further out of control. Lower fat diets are also not needed unless there is another health situation where you have to control fat intake.. or if SID is raging, you will also want to limit fat intake. However, once dog is stable, you can try adding rice to see if it is tolerable with your dog's digestive system.... in short to see if she can handle fiber, what kind and how much.
B12... over 80% of all dogs with EPI have insufficient B12. The B12 needs to be in the upper mid range (we like to recommend upper 500's to 600's)... normal or low normal B12 means your dog still needs to be supplemented. SOmetimes, even without the B12 blood test, vets will still put an EPI dog on B12 supplementation... since any excess B12 will just be peed out.. Typically sooner or later an EPI dog will eventually end up on B12. Please know that since EPI is a "chronic" condition...that the dog will need B12 supplementation for life... first to bring it up to upper mid range levels.... and then usually a reduced amount or frequency to "maintain" a good level. Without good B12, no matter how many things you do right with an EPI dog, if the B12 levels are not good, the dog will not flourish.
And last but probably the best tool you can ever have managing an EPI dog is to start keeping an EPI log (journal)... there are some good examples and templates here: https://epi4dogs.com/epi-log/
By keeping a log... and AFTER you initiate all the EPI protocol in the beginning (the enzymes, SID treatment as needed, B12, a diet that agrees with the dog) then make only one-change-at-a-time!!!! give the change 3 to 5 days, record the effects, even take poop pictures to show results...... by keeping a log like this it will really help you and your vet identify trends, what works with your dog and what doesn't.
Also.... always share with your vet anything and everything we suggest. Reagan will get the best care if everyone works together to help her
Hope this helps a little!