@rbennett You paint a small picture of the problem. It sounds like you are working with a PCP, not nephrologist. Things to consider: 1) What about the rest of your labs? There is usually a reason for CKD. 2) Creatinine eGFR tests often vary. 3)You were dehydrated at the time of testing. When tested, always be hydrated.4)You were taking creatinine supplements. This may typically lower temporarily your eGFR score. 5)Eating an overabundance of red reat could have an effect as well.6) Taking an ultrasound may alleviate some fear. Summarizing, you appear to have all the symptoms of a lower eGFR only because of your habits prior to testing. One eGFR is wakeup call, but the true measure of CKD is your "trend" over time. I would follow up with your doc suggestion with an ultrasound. On your next test be hydrated, avoid large meat quantities, make an appointment with a nephrologist, and look at the whole lab picture and not one lab score. Our mentor, @gingerw, can add to my response in case I missed something.

@rbennett Welcome to Mayo Clinic Connect. We often wander through life, not always considering how our lifestyle and habits can affect our overall well-being. Understanding how interconnected things are, @collegeprof has raised good points for you to look at. It is natural for our eGFR to decline with age, but it is prudent to watch for big changes.

Diet seems to be the biggest factor in what we can do to keep our kidneys healthy. Watching sodium, phosphorous, potassium and calcium intake helps. Limiting red meat, dairy, refined sugars may sound harsh, but it is in our best interest. I myself followed a strict renal diet for many years, and was able to stave off additional intervention for a long time.

I suggest you ask your primary care for a referral to a nephrologist, and establish a relationship. Be mindful of trends in your labwork, not just a single test. It sounds like you are no longer taking over-the-counter creatinine supplements?
Ginger