Hello, creatinine values depend on many factors. It can be elevated in serious conditions like acute or chronic renal failure or even in benign conditions. For example is your daughter a muscular athlete? If she is, then she ll have higher creatinine values than most other women of her age. You haven t provided urea values which are also important in kidney function evaluation. An increased urea/creatinine ratio suggests dehydration. That s what your doctor probably took into account when he spoke about dehydration. Of course, I can t be sure about that, because you ve not provided the results. Also, did she use any medication, did she have other symptoms besides tiredness? Did she pass red urine (bloody)? Does she have hypertension? Any swelling? Did she have decreased or excessive urine production? Since you ve not provided more information, the answer cannot be very specific. I suggest a repeat testing including a complete blood count, urea, creatinine, urinalysis, sodium, potassium, TSH. If everything is OK the she d need further evaluation for her tiredness. Kind Regards!