OP I had low Haematocrit last December, did my Full Blood Count test with an online provider. Here's what they had to say re that parameter, it might help:
About Haematocrit - Your haematocrit measures how much of your blood is made up of cells and is expressed as a percentage. Nearly all of the cells in your blood are red blood cells (RBCs).
A decreased haematocrit (Packed Cell Volume) indicates anaemia and further testing is required to determine the cause.
Many conditions can result in a low haematocrit including nutritional deficiencies in iron or vitamins, inflammatory conditions, cirrhosis of the liver, bone marrow disorders and more.
A low haematocrit needs to be interpreted in the context of other parameters within a full blood count, such as haemoglobin. If you are anaemic or have low haematocrit, then you should report this to your GP.
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I also had borderline low Haemoglobin raised white blood cells too. I had acute inflammation in my gut at the time (and my ferritin was raised) - diarrhoea, bleeding etc (sorry TMI!).
If you don't have inflammation then it may point to deficiencies. If your ferritin is very low (sounds like it is) then that could be the issue. Ferritin needs to be around 90+ Low ferritin can make you feel exhausted. I'm surprised your GP didn't recommend iron supplements or increasing your intake of red meat. It's certainly not something to be ignored!