Hello, thanks for your question today! I am Dr. Drew, and I am a licensed veterinarian. I'll be happy to help you in any way I can.
with a past history of diabetes, I'd be most concerned about weight loss that you've noticed,
since that is one of the top signs of diabetes.
As for the bloody stools, there are many causes for that,
you did not include any additional information such as the age of your cat,
but in elderly cats there is some concern about polyps or tumors in the colon (large intestine),
but less serious causes can include colitis (inflammation), which can be due to infections, parasites, dietary intolerance, allergy, etc.
blood clotting disorders, such as from ingestion of rodent poison or eating rodents that were already poisoned, could also cause bloody stools
if diabetes is not the cause of weight loss,
then other concerns include cancer, kidney disease, hyperthyroidism, or heart disease.
was she losing weight at her exam 2 months ago?
ok, so if she was not losing weight then, but is now, then we can't automatically assume that the blood tests would necessarily represent what is happening right now.
straining suggests irritation and inflammation in the intestine,
which fits with all of what I mentioned above,
it doesn't really narrow the causes down any further.
sometimes fiber in the diet may be helpful,
you can give her mashed green peas or canned pumpkin with her food,
or 1/2 teaspoon of psyllium powder daily
well, that would be safest for her.
if there's any actual stool that she's produced, besides the blood, then you can bring that so it can be tested for parasites.
you are very welcome. Best wishes to you both.