Hello. My name is***** have been a veterinarian for 11 years. I am sorry to hear that Loui has chronic diarrhea.
I understand the financial concerns of a veterinary visit. Please understand that the information provided on this site is just general information. We legally cannot diagnose or prescribe medications. I recommend saving money as quickly as possible to have your cat seen. In the mean time, I will give you some basic information on diarrhea and ways to attempt to decrease it.
Diarrhea for a month is a significant medical condition. If it is parasites, then Loui will need medication to get rid of the them, but a fecal sample should be checked to make sure that you are treating for the right parasite.
Some things that can be done is feeding a bland diet for a few days and increasing fiber in the diet. A bland diet usually is composed of 2-3 parts cooked rice and 1 part boiled hamburger or chicken. For example if you feed 1 cup of the mixture, you would feed 3/4 cup cooked rice and 1/4 cup boiled meat. Increasing fiber can be done with either canned pumpkin (not pumpkin pie filling) or Metamucil or Benefiber supplements.
Your veterinarian may be willing to send home medication for Loui and any other animals in the house for treatment, but they would have had to have been seen relatively recently or at least within the last year in most cases. Asking is never a problem, but if they say no, it is likely because Loui needs an exam in order to have a prescription given.
If tapeworms is the problem (although usually that is not the cause of chronic diarrhea), then you will likely need to treat for fleas as well. Cats get tapeworms from ingesting fleas when they groom and from eating things such as rabbits, mice, or other rodents.
If this has not answered your question, please let me know so that I can be more specific to your question.
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I hope Loui feels better soon!