Walking into an appointment and asking to "test everything" rarely goes well. Walking in able to say why you are asking about a specific test goes much better.
This page lists the tests commonly involved in investigating fatigue and what each is looking for. It is a guide to the conversation, not a shopping list — your GP decides what is appropriate for you, and they will be considering things this page cannot.
The usual first round
Full blood count
The standard starting point. Shows anaemia, signs of infection, and abnormalities in your white cells and platelets. Broad rather than deep.
Iron studies, including ferritin
The one to ask for by name. A full blood count can be completely normal while your iron stores are depleted — anaemia is the late stage, not the first sign. Ferritin measures the stores themselves.
Especially relevant if you menstruate, are pregnant, eat little or no red meat, or donate blood.
One nuance worth knowing: ferritin rises with inflammation, so a normal result alongside a raised CRP does not entirely rule out low iron.
Vitamin B12 and folate
Both cause fatigue when low. Higher risk on a vegan or vegetarian diet, over 50, or on long-term metformin or reflux medication, all of which reduce B12 absorption.
Thyroid function (TSH)
An underactive thyroid is a classic cause of fatigue, often alongside cold intolerance, weight gain, dry skin and low mood. TSH is the usual screen; free T4 is sometimes added.
Vitamin D
Common to be low in Australia, particularly for indoor workers, people who cover up, and darker skin tones in southern states. Rebating for this test depends on specific criteria here, so ask your GP whether you meet them.
Blood glucose or HbA1c
Both diabetes and pre-diabetes cause fatigue well before anything more obvious. HbA1c reflects the last few months rather than that morning.
Kidney and liver function
Usually included. Both organs cause fatigue when not working well, often with few other early signs.
Worth raising if the first round is clear
Coeliac serology
Fatigue is one of the most common presenting symptoms, frequently without gut complaints. Critical practical point: you must be eating gluten regularly for the test to be valid. Cutting it out beforehand produces a false negative and wastes the test.
CRP or ESR
Markers of inflammation. Non-specific, but they tell your GP whether something inflammatory is running in the background.
Calcium
Abnormal levels cause fatigue and are easy to overlook.
Sleep study
Not a blood test, but often the answer when bloods are clear — particularly with snoring, morning headaches, or daytime sleepiness. Sleep apnoea is invisible to bloods.
How to ask
Lead with the symptom and the reason, not the test name:
"I've been exhausted for three months, it isn't improving with sleep, and my periods are heavy. Could we check my iron stores including ferritin, and my thyroid?"
That gives your GP the clinical reasoning to work with. Compare it to "can I get a full panel", which gives them nothing.
Other things that help: ask for your actual numbers rather than "normal"; mention if fatigue tracks your cycle; mention any medication you take long-term; and say plainly how much it is affecting your work and life.
Once you have results
If something is low, treat it under medical guidance and re-test. Iron in particular should not be self-supplemented — too much accumulates and causes harm, which we cover in can you take too many supplements.
If everything is normal, that is genuinely useful information, not a dead end. What to look at when bloods come back normal covers where the answer usually is.
If you are correcting a deficiency, timing affects absorption more than people expect — iron with vitamin C rather than tea, fat-soluble vitamins with a meal. See the supplement timing chart.
Where we fit, and where we do not
We sell supplements. We do not sell blood tests, diagnoses or treatment for deficiencies, and this page is not a substitute for any of them.
Where a foundation genuinely helps is covering ordinary dietary gaps — Daily Essentials is built for that. Correcting a diagnosed deficiency is your GP's job, and they will want to re-test to confirm it worked. Guessing at it with supplements is how people stay tired for another six months.
Who wrote this
Written by Daniel, founder of Nutritions Lab. Nobody here is a doctor or a pathologist. This page reflects the tests commonly involved in a standard fatigue workup, written so you can have a more useful conversation — not so you can interpret results yourself. Interpretation is genuinely difficult and depends on your history, and that is what your GP is for.
Our approach is in our editorial policy. Full context in why am I always tired.
General information only, not medical advice. Do not use this page to self-diagnose or to interpret your own results.
