I am sorry Annie is unwell.
Firstly, you need to ascertain the precise diagnosis, chronic kidney disease and cystitis are two very different conditions.
Both with significantly different treatments and prognoses.
Blood in the urine can be caused by many things including kidney disease, kidney tumours, kidney infection, bladder inflammation and less commonly bladder infection.
So the bloody urine needs to be put into context with the previous problems from January when Fortekor was prescribed.
I would advise that a full assessment of her renal function (blood tests and urinalysis as well as blood pressure measurement) is performed as well as ruling in or out pathology in the bladder (cystitis) it needs to be clear whether two separate conditions are present or the same problem is causing the blood in the urine.
I am not sure what you are referencing when you say her blood result should be 38 and not 15.
Subcutaneous fluid administration by owners at home is not allowed to be done here in the UK.
If the condition that is affecting Annie is able to be managed then there should be no need for continued use of SC fluids. Certainly, receiving fluids through an IV line is much more effective.
Annie needs to get a precise diagnosis, the chronic kidney disease if present needs to be staged to provide you with a better realistic prognosis. Other therapy can be used if appropriate (especially if the blood pressure is high or the phosphate levels in the blood are elevated)
The blood in the urine needs to be diagnosed and its cause identified and treated
The most common cause of cystitis in cats is feline idiopathic cystitis which is a non infective inflammation, causing swelling and pain and bleeding of the bladder wall.
Stress is considered the most likely trigger with pain being the priority to control
However, given the previous diagnosis of kidney disease it is important to ensure the bloody urine isn't related to the kidney disease as this may indicate more serious disease.
Unfortunately though, the regulations regarding subcutaneous fluid administration are different between here and the USA
Good luck and I hope this all makes sense