Hello to the community i. I am resident of Greece but recently moved in UK. I am 27 yo male , i don't smoke, i don't do drugs or taking any testosterone replacement and don't drink too often (1 time per month and fewer). So all started back in 2019 when my hematocrit was 51% , hemoglobin 16 gr/dL , rbc 5.7 M/μl , wbc 7.8 K/μl , platelets 320 K/μl and ferritin 26ng/ml. The general doctor told me to take a look for another doctor but i never checked it. I am blood donor so in November of 2022 i donated blood and the hematocrit that moment was 50%. Then in January i did a check up and the results was 49.7% , hemoglobin 16.2 gr/dL , rbc 5.77 M/μl , wbc 9.4 K/μl , platelets 336 K/μl and ferritin 15ng/ml. And TSH was little more than highest level so i started a pill. Then they told me again to check it on someone specialist. So i did because i was feeling fatigue and he told me to he can't do any test until hemoglobin go above 18 gr/dL. But he never mentioned to take any iron supplement but encouraged me to donate blood as many as possible i am allowed to donate per year and to keep taking the pill for thyroid. So i did i donated again in the late of February. Then in May of 2023 i did again a chack up to check my TSH levels but with some blood test again. So the results for the blood was hematocrit 51.5% , hemoglobin 16.9 gr/dL , rbc 5.9 M/μl , wbc 7.8 K/μl , platelets 290 K/μl and ferritin 13.5ng/ml. And the general doctor and the specialist again told me that may i have something it's called erythrocitocis and i tend to have higher levels than the normal person. So the same keep donating blood and nothing for iron supplement. Then I moved in UK, i donated blood in the start of June. After a month and a half i had some chest pain so i went to A&E , they didn't find anything and contact with my GP to prescribe some blood test . So i did again blood test ik the 1st of August and the results was quite weird for me. My hematocrit level was 46% ,hemoglobin 15.2g/L , rbc 5.62 1012/L , wbc 7.5 109/L , platelets 337 10*9/L and ferritin 9ng/ml. So i booked an appointment with GP doctor(not specialist maybe a general doctor) to discuss about the blood results. So the thing is that the doctor only took a look on the UK blood test results and not the previous i bring with me from Greece. The doctor suggested me to take iron supplement (210 mg ferrous fumarate) for 6 months. So my question is how a person who has constantly high levels of hematocrit and hemoglobin, suddenly getting more normal levels of them ( but still feel fatigue ) . I didnt have any external bleeding or from nose/mouth/ stools. How can i trusted the doctor and take iron supplement,who doesn't have my full medical history, only based on the last results? Just trying to fiqure out why the last 3 blood test are completely different (2 same , 1 different). My food intake hasn't change taht much, maybe little less lentils than usual but still eating iron in my meals. Sorry for my long story, but need to speak with someone who can suggest me something!! Have a great night!!!