In other words chronic tiredness is a severe problem and something you need to address. But with so many potential causes and with such subjective criteria it can be highly difficult to diagnose. You might think that it's all in your head, and in fact you might at first not even realize that you have been tireder as it can come on slowly. Then there are many things that you might consider to be causing it – it could be the imminent onset of a cold, or a hangover from a previous cold or illness. It could be depression. It could be insomnia or sleep apnea. It could be anemia, diabetes or hypothyroidism. Chances are that if you go to a doctor they will give you a blood test and then tell you to get more sleep or ask if you might be suffering from depression. This can then be a highly distressing response as it leaves you no closer to combating the problem.
Here's something they and you might not have considered – allergies – and these are responsible for many unexplained cases of tiredness and lethargy. Whether it's an allergy to food, to pollen or to something else entirely. Once you realize this and get to the bottom of what is actually causing your allergic reaction, then you can start to address the problem and feel less tired – and if you've been not feeling yourself for a while then that can seem nothing short of a miracle.