Pre Cork Marathon Bloods


I made a visit to the vampire on the Wednesday before the Cork Marathon. I picked the Wednesday as I didn’t want to know the results before the race. 

Bad Blood

My dose of Thyroxine (T4) had been reduced from 175mcg to 150mcg from the last time I had the blood test because I was verging on hyperthyroid. The reduction in dose appears to have had an effect on my red blood cell count. My haematocrit has dropped from 47% to 43% and my haemoglobin from 16g/dL to 15g/dL. My Ferritin is pretty much unchanged at 36 ng/ml which kind of rules out an iron issue.  

Why Would Thyroxine Impact Red Blood Cells?

Thyroid hormones play a role in red blood cell production. They increase secretion of EPO and increase the repletion of HIF-1a. EPO is the hormone that directly increases red blood cell production. HIF-1a (Hypoxia Inducible Factor) is a transcription factor that is increased in response to reduced oxygen levels. More HIF-1 means more red blood cells essentially. 


Could thyroxine be being used for doping? Well based on my inadvertent dosing trial it probably could improve haematological parameters, although it’s probably not exactly a good idea. I did not feel any better on the 175mcg, in fact I felt a little worse. I didn’t run any better.  

What am I on


Levothyroxine 150mcg daily (On Prescription)

Ventolin 200mcg before running   (On Prescription)

Galfer 1 per day

Actice Iron 1 per day

Feosol Complete 1 per day

Sona Acidophilus 3-4 per day

Vitamin D 1500IU per day