What are some potential causes of chronic fatigue? i've been tested for anaemia, thyroid disorders, mononucleosis and haemochromatosis, but no answer.

Innumerable: Check for diabetes, depression, anxiety, infections (hiv, hepatitis, etc.), sleep apnea, and other causes. If you already been to your fp to start exploring potential causes and come up empty-handed; go back. Your doctor is as puzzled and curious as you are to figure out the puzzle, and they have the first few sets of answers to build on. The value of your doc is in the continuity of care.

More Leaves to Turn: Fatigue unfortunately carries a significant amount of possible causes. It sounds as if your doctors are going through the process of eliminating some of the likely players. In the small space we have here, if the above mentioned work-ups were negative....I would take a close look at your bmi or body mass index. Food choices can make a big difference in how you feel hr to hr during the day.