Rising BUN and Creatinine Levels: Should You Worry About Kidney Health?

If BUN and creatinine levels are continuously rising (but still within the normal range), does this indicate a problem with the kidneys?

Hello Doctor: I had a blood test in November 2017, which showed a BUN of 6 and a creatinine level of 9.
In August 2018, I had another blood test, and my BUN increased to 9.5, while my creatinine rose to 1.01.
Three months later, in November 2018, I had a follow-up test, and my BUN increased again to 11.8, with creatinine rising to 1.11.
Although these values are still within the normal range and there is no proteinuria, my doctor said this is considered normal.
However, seeing the continuous rise in BUN and creatinine still makes me worry about potential kidney issues.
It is worth mentioning that I started a weight loss program in July 2018, with a nutritionist changing my eating habits, and I began strength training and aerobic exercise (once a day for each).
Recently, due to academic pressures, I have been participating in exercise less frequently.
I am unsure if this could be related to my exercise habits (as I previously did very little exercise).
Additionally, I had a kidney stone in the past, but it has been treated.
I would like to ask the doctor: 1.
Does the continuous rise in BUN and creatinine indicate a kidney problem? 2.
Are the increases in these values related to changes in exercise and diet? 3.
Should I see a nephrologist for further evaluation? I am really worried, as I am only 22 years old and fear developing chronic kidney disease.

Niming, 20~29 year old female. Ask Date: 2018/11/20

Dr. Wu Hongjie reply Internal Medicine

1.
BUN and creatinine (CRE) have standard values established by each laboratory.
As long as the values are within the normal range (e.g., CRE: 0.7-1.3), the results indicate that they fall within the normal limits.
Fluctuations in these values can be significantly influenced by daily water intake, protein consumption, and blood loss, among other factors.
2.
These values are also related to daily water intake, protein consumption, excessive exercise leading to dehydration, or rhabdomyolysis.
3.
If there are any concerns, it is advisable to conduct further tests.
However, if other physicians have already evaluated and determined that there are no abnormalities, then monitoring the situation is sufficient.
Wishing you good health.

Reply Date: 2018/11/20

More Info

When it comes to rising levels of Blood Urea Nitrogen (BUN) and creatinine, it's understandable to feel concerned about kidney health. Your situation, with BUN levels increasing from 6 to 11.8 and creatinine levels from 0.9 to 1.11 over a period of time, raises important questions about kidney function. Let's break down your concerns and provide some clarity.

1. Understanding BUN and Creatinine Levels: BUN and creatinine are both waste products filtered out of the blood by the kidneys. BUN is a measure of nitrogen in the blood that comes from the waste product urea, while creatinine is a byproduct of muscle metabolism. In healthy individuals, these levels are relatively stable. A gradual increase in both can indicate a decline in kidney function, but it is essential to consider the context of these changes.

2. Interpreting Your Results: Your BUN and creatinine levels, while rising, are still within the normal range. Normal ranges can vary slightly depending on the laboratory, but generally, BUN levels are considered normal between 7-20 mg/dL and creatinine levels between 0.6-1.2 mg/dL for most adults. The fact that you have not experienced proteinuria (the presence of excess protein in urine) is a positive sign, as proteinuria is often an early indicator of kidney damage.

3. Impact of Diet and Exercise: Changes in diet and exercise can significantly affect kidney function markers. A high-protein diet, for instance, can lead to elevated BUN levels, as the body breaks down protein into urea. If you've recently altered your diet or exercise routine, this could explain some fluctuations in your BUN levels. Additionally, dehydration from exercise or dietary changes can also lead to temporary increases in these markers. However, since you mentioned that you have been less active due to academic pressures, this could also contribute to changes in your kidney function tests.

4. Previous Kidney Stones: Having a history of kidney stones does not necessarily indicate ongoing kidney issues, especially if they have been treated successfully. However, it is essential to maintain adequate hydration and follow dietary recommendations to prevent recurrence, which can sometimes affect kidney function.

5. When to Seek Further Evaluation: Given your concerns and the gradual rise in your BUN and creatinine levels, it would be prudent to consult a nephrologist (kidney specialist) for further evaluation. They may recommend additional tests, such as a urinalysis, urine protein tests, or imaging studies, to assess kidney structure and function more thoroughly. Regular monitoring of kidney function is crucial, especially if you have risk factors or a family history of kidney disease.

6. Lifestyle Recommendations: Continue to focus on a balanced diet, staying well-hydrated, and maintaining a regular exercise routine. If you are considering dietary changes, particularly regarding protein intake, consult with a nutritionist to ensure your diet supports your overall health without putting undue stress on your kidneys.

In summary, while the rising levels of BUN and creatinine can be concerning, they are still within normal limits, and the absence of proteinuria is reassuring. However, given your history and lifestyle changes, it would be wise to follow up with a healthcare provider for a comprehensive assessment. Regular monitoring and proactive management can help ensure that your kidney health remains stable as you continue to make lifestyle changes.

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