ROFL...
Actually, chronic tiredness/fatigue is a symptom of about 300 different things. Now, only about 50 of which are common, then next 100 or so, somewhat common, the next 50 or so fairly rare, and the last 100 or so very rare.
In the first 50 you'll find things like
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- Persistent Sleep deprivation (most common, statistically most people don't get enough sleep. Sleep dep has it's own range of 50 or so common causes and can range from minor -consistantly missing an hour or two of necessary sleep-, to severe -only getting a small fraction of necessary sleep. The range of causes is fairly wide, from choice/situational to neurological; like insomnia... and then has about 100 or so less common causes, and about 50 rare causes)
- Recovering from / relapsing illness (from colds/flus, to walking pneumonia, to various form of bacterial, viral, or fungal infections of various systems or organs)
- Hormonal imbalances (again, category 1: in women often thyroid, birth control pill related)
- Pregnancy
- Category 1 nutritional deficiencies (aka common ones; anemia, calcium, dieting, anorexia, bulemia)
- Anxiety
- Depression
- chronic pain from old injuries
- etc. for a list totally out to apx 50 causes, some of which have their own 50-100 common causes
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The next 100 fairly common = things like:
- certain cancers (of which there are several hundred)
- structural problems/ damage to certain organs (type 2 diabetes, common lymphatic problems, common heart problems, common respiratory problems, etc.)
- less common illnesses (bacterial, viral, fungal -you don't find parasites until the next level of 'fairly rare' causes in this country)
- category 2 (less common) nutritional deficiencies, usually related to common structural damage of organs, or long term dietary choices
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The next 50 of fairly rare (less than 10% of the population) causes you'll find 1/2 of yours, so I'll put them at the top
- very mild allergies or sensitivities or difficulty processing (absorb or excrete... BUT not impossible to process, absorb, or excrete) certain common foods or components in foods, BUT this includes ALL types of foods; grains, legumes, proteins, amino acids, dairies, animal lipids, plant lipids, sugars, copper, iron, magnesium, etc. IN THE NEXT LEVEL DOWN THESE ARE MUCH STRONGER reactions and ALL of these have "names", like Celiacs, Wilson's, etc. In this level, they're 'annoying' but not dangerous to health, just quality of life... producing things like tiredness.
- "Common" parasitic infection (worms, usually)
- "Common" neurological disorders (adhd, ASD, anxiety disorders, sleep disorders,
- "Less Common" organ damage or structural issues (Hashimoto's, arterial stenosis, etc.)
- HIV+
- etc.
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50 or so RARE causes (in this country)
- Celiacs, Wilsons, Kwashiorkor and other rare nutritional processing, absorption, or excretion
- Malaria
- (and a whole host of other 'rare' parasites from leishmania to giardia to...)
- Amoebas (and other single cell or protozoen infection)
- Radiation poisoning
- Heavy metal toxicity
- etc
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Now... the thing is... the ORDER of rareity changes geographically speaking. In a certain belt of the world, if someone was feeling tired all the time the leap wouldn't be to lack of sleep and various causes as the knee jerk reaction, but Malaria. In other parts, knee jerk would be HIV+.
Doctors are JUST like parents. They go down "the list" of things in most common order. 99 times out of 100 if a patient says "I'm tired ALL the time." if asked, they aren't getting enough sleep. Which isn't a "simple" answer, because there are a good 50-100 causes of not getting enough sleep, or having interrupted sleep (restless leg, urinary issues, nightmares, panic attacks, thirst, there are dozens and dozens of reasons why a person is having interrupted sleep from a medical perspective NOT including 'common' things like children).
If your baby was crying, you wouldn't immediately call the police because an intruder had come in and pinched them, nor take them to the ER to evaluate for seizures. Nope. Instead you'd touch their diaper, pick them up, offer them some food. (3 most common reasons why a baby cries) if they're comforted, dry, and not hungry but STILL upset, then you look for other causes (fever, teething, gas, etc.). if it's STILL not obvious why they're upset, then you keep going down the list (looking for bumps or bruises, twisted clothing, etc.)
Fatigue is a symptom of over 500 things. Immediately jumping to a fairly rare nutritional problem is the EXACT SAME THING as calling the police or rushing to the ER... it's just not the smart thing to do.
Granted, I've had the misfortune to run across a few terrible doctors, but to make the leap from fatigue to gluten and heavy metals is a pretty HUGE leap over a couple hundred other causes.