I am a 46-year-old white female suffering from IBS symptoms, tiredness and occasional palpitations over the last year and a half. Also diastolic BP between 89 and 90. Over autumn I've had recurring cold/ENT symptoms. I have been investigated over the last 12 months with abdominal ultrasounds, endoscopy, CT and MRI all of which showed no abnormalities. However, recent blood tests returned GFR calculated abbreviated MDRD 86. (Previous tests 6 months and 11 months ago, above 90)
Is there any significance in this or anything else that needs investigating? Or could it be normal?
My serum creatinine is 68umol/L (previously 63, and before that 65)
Other results as current:
Serum sodium 143mmol/L
Serum potassium 4.2mmol/L
Serum urea 3.1mmol/L
Serum calcium 2.46mmol/L
Corrected serum calcium 2.36mmol/L
Serum inorganic phosphate 1.09mmol/L
Serum total protein 69g/L
Serum albumin 45g/L
Serum alkaline phosphatase 48g/L

FBC and LFT also within normal ranges

Please could you confirm whether the below 90 GFR should concern me?