I understand the concern with not knowing when kidneys are failing. I have had to learn my body's signals that aren't very evident. I also struggle with bacterial infections since one of my surgeries, that I don't get overt uti symptoms of.
Here's what I've done to help me try and get in front if it...
1) I note any increase in my fatigue level . That's one of my key tip offs. I call them red flags which have me take notice and step up my response...
I have fatigue anyway
but anything that steps
it up becomes a red flag for me.
2) loss of appetite
3) increase waking at night to pee
4) irritability
5) fuzzy thinking increase
6) swelling... legs , hands with tight rings, face, puffy eyes
7) change in urine color , clarity and if it has foam
8) oddly craving carbs or sugar unexpectedly
9) food makes me nauseous .. gagging
10) shortness of breath

When I notice these red flags , I do a home uti type test, if protein is increased , red blood cells etc, anything out of the normal range I follow up with call or email to my Dr. I use a test that is a simple urine test but test multiple factors
I also start monitoring my temp. Significant drop ( I drop low before a high fever) or anything over 99 , is a red flag for me .
My husband is also familiar with the red flags, and will notice and prompt me to pay attention . I sometimes just plug on... ignoring that I'm feeling worse the usual.
Oddly my dog now alerts me as well by smelling breath when things are going bad. If he starts smelling my breath , I pay attention and I start testing . ( usually test in morning and at night if I'm monitoring. Or if i have signifcant symptoms) He helps me catch it early as well.
After two hospitalizations in 18 months for sepsis with organ failure... I've been able to head off and keep out of the danger areas .
Hope this gives you some ideas. It's learning your body and just being present enough to take notice.
It actually helps me to relax a little more and live my life fully.

I use Trader Joes '21 Seasoning Salute' on everything!