Blood Tests to Ask For When You Are Tired All the Time
Ask for a short first-round list. Nine items: full blood count, ferritin with transferrin saturation, TSH with free T4, thyroid antibodies, B12, HbA1c, CRP, liver and kidney tests, coeliac screen. Already have a printout? Check it against the list. No printout yet? Take the list into the appointment, and say it out loud.
Say this at the appointment, then write down three things
Say: "I am tired all the time. I would like to go through the first-round tests for that: full blood count, ferritin with transferrin saturation, TSH with free T4, B12, HbA1c, CRP, liver and kidney tests, and a coeliac screen. Which of these have I had, and which have I not?"
The last question does the work. "Your blood is fine" becomes a list with ticks and gaps.
For every result, write down three things: your number, the date of the draw, and the lab's limits printed beside your number, the lower one especially. Nobody will record these for you, and you need them later to compare one result with the next.
Say which supplements and medicines you take, including the ones you buy yourself. Some change a result for a while: iron tablets lift ferritin, and certain vitamins can distort some tests. Do not stop anything on your own. Ask whoever orders the tests what to do before the draw.
This list is what is worth asking for, not a national rule. What counts as a first-round panel differs between countries and between clinics, and this page is not matched to any one country's guideline.
Find your case
| Your number | What it means | What to ask for | First step |
|---|---|---|---|
| Full blood count | Counts the cells in your blood: red cells, which carry oxygen, white cells, which fight infection, and platelets, which help clotting. | "Full blood count", and ask to see the red cell results on the printout | Iron in storage, thyroid function, blood sugar and B12 level. None of these are measured by it. |
| Ferritin and transferrin saturation | Ferritin is the iron your body keeps in storage. Transferrin saturation shows how much of the iron in transit is loaded and ready to use. | "Ferritin and transferrin saturation", named separately from "iron levels" | Stores that are too low for you while still inside the lab's limits. The limits come from a population, not from you. |
| TSH, free T4, and thyroid antibodies if TSH is borderline | TSH is the signal your brain sends to the thyroid. Free T4 is the thyroid hormone circulating in the blood. Antibodies show whether the body is attacking the thyroid by mistake. | "TSH with free T4", and "thyroid antibodies" if TSH sits near the edge of the limits | An autoimmune process in the thyroid can be present while TSH reads normal. Only the antibody test looks for it. |
| B12 and HbA1c | B12 is a vitamin your nerves and red cells need. HbA1c is your average blood sugar over the past few months; fasting glucose is a single morning reading. | "B12" and "HbA1c or fasting glucose" | A B12 result inside the limits can still sit at the low end of them. A single glucose reading can miss a pattern that HbA1c would catch. |
| CRP, and liver and kidney tests | CRP is a protein the liver makes when there is inflammation anywhere in the body. Liver and kidney tests show whether those organs are clearing waste normally. | "CRP", "liver function tests" and "kidney function tests" | Low-grade or recent inflammation can be missed by one reading. Normal organ tests say nothing about hormones or iron. |
| Coeliac screen | Looks for antibodies that appear when gluten triggers the immune system to damage the lining of the gut, which then absorbs less iron and B12. | "Coeliac screen", and say you are still eating gluten | The test only works while gluten is in your diet. A normal result after cutting it out proves little. |
What a full blood count cannot see
A full blood count counts cells: how many red cells you have, how big they are, how much oxygen-carrying protein each holds. That is a useful question with a narrow answer.
The body defends that count. When iron runs short, it spends its storage first, so the red cells stay steady while the stores empty. The count reads normal for as long as the storage lasts. Ferritin, the iron your body keeps in storage, is the test that checks the stores. The full blood count does not include it.
Thyroid function, blood sugar, B12 level and inflammation are not on a blood count either. "Your blood is normal" usually means one test was looked at, and it passed.
Appointments are short, and the cheapest first order is the one that brings back the fewest follow-up questions. That is a system saving time. It is rarely a judgement by the clinician and never a judgement about you. It is why you leave with a general "fine" instead of a list.
The list here is what is worth asking about when tiredness has no obvious cause. Countries and clinics draw this line in different places, so some items may be offered at other points in your care. Asking is allowed. "That one is not needed" is also an answer, and it comes with a reason you can write down.
What to do when TSH is normal and you still feel unwell
TSH is the signal your brain sends to the thyroid, the small gland in your neck that sets the pace of your energy use. When the thyroid slows down, the brain pushes harder and TSH rises. A normal TSH means that push is within the lab's limits.
Those limits are built from a large group of people. They describe where most of them sit. They say nothing about where you sit, or whether your own number has moved over the years. Two women with the same result can be in very different places.
Ask for free T4 alongside TSH. Free T4 is the thyroid hormone itself, the part circulating unattached and available to your tissues. TSH shows what the brain is asking for, and free T4 shows what arrived.
If TSH is borderline, ask for thyroid antibodies. They point to an autoimmune process, where the body attacks its own tissue by mistake. That process can be present while TSH is still inside the limits, which is why the antibody test is a separate request. A positive result is no diagnosis by itself. It is a reason for the clinician to watch the thyroid over time and decide what comes next.
For the longer version of each half of this, read Mildly Raised TSH: Does It Go Away on Its Own? and Hashimoto's With a Normal TSH: Can It Still Cause Symptoms?.
Ferritin follows the same logic. A result inside the lab's limits shows your stores are not empty by that lab's standard. It does not guarantee they are enough for you. Write down the number and the date: two results of your own tell you more than one result against a population.
What to leave out of the first round
Sex hormones, such as oestrogen, FSH and progesterone, rise and fall across the menstrual cycle, sometimes within a few days. A single draw is a snapshot of one moment. Without the day of your cycle the result is hard to read, and a normal-looking number on the wrong day tells you little. Ordering them with everything else often produces noise instead of an answer. If you suspect your cycle is part of the story, read Can a Blood Test Show Perimenopause? It Depends on Your Age before asking.
Cortisol, the hormone your body uses to handle stress and wake you up, follows a daily curve. It is high in the morning and lower later. A single blood draw at a convenient hour lands on one point of that curve and says little about the rest. Whether a one-off test can show anything useful here is argued about, and Cortisol Symptoms and Adrenal Fatigue: What Testing Can Prove lays out what a test can and cannot prove.
Vitamin D is a separate question. Whether checking and correcting it helps with tiredness is argued about, and this page has no evidence to settle it either way. Ask for it when your clinician can name a reason, and do not add it by default because it is easy to order. If it is ordered, ask what decision the result would change.
All three belong in a second conversation, with a reason attached. The first round is the cheap, broad sweep that tells you which direction to look in.
What to say when the answer is "everything is normal"
A normal result answers one question: was this value outside the lab's limits on this day? It does not say whether you are well.
So turn it back into a question. Say: "Thank you. What has this set of tests ruled out, and what has it not?" If the answer is vague, ask for the list in writing, or ask the clinician to point at each line on the printout.
Then ask what comes next if the tiredness continues. Useful versions are: "When would you repeat these?" and "Which of these would you want to look at again if I am still tired?" Write down the reply and the date, next to your numbers.
If you have older printouts, compare. A number that has drifted down across several years can sit inside the limits the whole way, and the limits will not flag it. Only you, holding both pieces of paper, will see the movement.
The sentence you leave with changes. "You are just tired" becomes "these items are checked, these are not, and this is when we look again." That does not explain the tiredness yet. It is a record that the search was real, and the next appointment can start from it.
What to do with this
- Name the tests aloud: full blood count, ferritin with transferrin saturation, TSH with free T4, B12, HbA1c, CRP, liver and kidney tests, coeliac screen
- Write down each result, its date and the lab's limits beside it
- Ask thyroid antibodies to be added when TSH sits near the edge of the limits
- Hold off on sex hormones and cortisol until a reason and a day of the cycle can be named
- Ask what the set of tests has ruled out and what it has not, and when it should be repeated
Questions people also ask
Is a full blood count enough to rule out causes of tiredness?
It answers a narrow question: how your blood cells look today. It does not measure iron in storage, thyroid function, blood sugar or B12. A normal result means those cells looked fine, and the other items on the list are still open.
Should I ask for every hormone test at once?
Usually no. Sex hormones change with the day of the cycle and cortisol changes with the time of day, so a single draw of each is often hard to read. The first round is the broader list above. Ask about hormones as a second step, with the cycle day or time of day agreed in advance.
Do I need a vitamin D test when I am tired?
Whether vitamin D explains tiredness is argued about, and this page has no evidence to settle it. Ask for it when your clinician can name a reason in your case, and ask what decision the result would change, rather than adding it by default.
This article is information, not medical advice, diagnosis or treatment. Reference ranges, doses and protocols differ between people and between laboratories. Talk to a qualified clinician before changing anything about your care.