Fibromyalgia symptoms are pain across your whole body, a tiredness that sleep does not fix, and a head that feels slow. It all sits in your body. Just not in your blood. In a study of 2,369 patients, the diagnosis took 6.4 years on average (PMID 31174818).
So let me start with the honest sentence rather than the one that sells better. No blood test can show fibromyalgia. There is no value that lights up, no marker that confirms it.
What blood testing can do is check a number of conditions that closely resemble it. An underactive thyroid, a low iron, an inflammatory disease. That sounds modest, but it is exactly the step those years are often spent waiting for.
What are the fibromyalgia symptoms in women?
The core is chronic pain across your whole body, left and right, above and below your waist, lasting longer than three months. Add fatigue, sleep that does not restore, and trouble with concentration and memory. In women these complaints are often looked at separately, so the pattern underneath goes unnoticed.
Here is what makes it hard: none of these complaints is remarkable on its own. Everyone gets tired and everyone has pain sometimes. It is the combination, and above all the duration, that tells a different story.
Signals that tend to appear together:
- Pain that moves, your shoulders today, your hips next week.
- Waking as though you never slept, even after eight hours.
- Fatigue out of proportion to what your day actually held.
- Losing words or losing the thread, commonly called fibro fog.
- Sensitivity to sound, light, cold or touch.
- Often alongside irritable bowel, headaches or a low period.
Those last two are interesting. They fit the idea that fibromyalgia is not a disease of your muscles, but of the way your nervous system processes pain.
Why does a fibromyalgia diagnosis take so long?
Because no test exists that settles it. The complaints are subjective, they overlap with dozens of other things, and the criteria have changed several times since 1990. That is a problem of research and guidelines, not of the GP sitting across from you.
Look at how those criteria developed. In 1990 the American College of Rheumatology put tender points at the centre: tenderness at 11 or more of 18 fixed points, alongside widespread pain. That combination had a sensitivity of 88.4 percent and a specificity of 81.1 percent (PMID 2306288).
In 2010 the tender point examination disappeared. The new criteria used a pain index and a symptom severity score, with no physical tender point exam (PMID 20461783). A further revision followed in 2016 (PMID 27916278).
Three different yardsticks in 26 years. When the definition itself moves, the diagnosis moves with it.
Is it true that fibromyalgia mostly affects women?
Yes, though less dramatically than the familiar nine-in-ten figure suggests. How lopsided the ratio looks turns out to depend on which set of criteria you happen to use, and the gap between those sets is large. I find this the most honest and the most underrated point in the whole subject.
In one population study the same people were assessed against three criteria sets. The female to male ratio was 13.7 to 1 under the 1990 tender point criteria, 4.8 to 1 under the 2010 criteria, and 2.3 to 1 under the modified version of those (PMID 25323744).
The same people. A different yardstick. An entirely different picture of who has this condition.
Prevalence shifted just as much, from 1.7 percent to 1.2 percent to 5.4 percent (PMID 25323744). So women are genuinely over-represented, but part of that nine-in-ten looks like an artefact of a tender point exam that picked up men less well. That is not a footnote. For decades it shaped who came into view and who did not.
Can blood tests prove or rule out fibromyalgia?
No. There is no blood value that proves fibromyalgia, and none that rules it out. A normal result does not mean your symptoms are not there. Fibromyalgia is established clinically, on your history and your physical examination, not on a number from the lab.
The role of blood testing here is a different one, and it is clearly defined: checking whether something else is playing that resembles fibromyalgia. An underactive thyroid also causes pain and fatigue. So does a low ferritin. Those things are treatable, and that is why they get checked.
There is a nuance here that often drops out. For a long time fibromyalgia counted as a diagnosis of exclusion: the label could only fall once everything else had been ruled out. The 2016 revision took that requirement out (PMID 27916278). Fibromyalgia can exist alongside rheumatoid arthritis or a thyroid condition, not only after them.
That is not word play. It means an abnormal thyroid value does not take your fibromyalgia away, and a normal result does not confirm it.
Which conditions resemble fibromyalgia?
A number of conditions cause pain and fatigue that can closely resemble fibromyalgia. For some of them a blood value points the way, which is exactly why they get checked first. Below are the conditions most often looked at in chronic pain, with the value that goes with each.
| Condition | What it is | Which blood value touches it |
|---|---|---|
| Underactive thyroid | Your thyroid makes too little hormone | TSH and free T4 |
| Anaemia or iron deficiency | Too little haemoglobin or an empty iron store | Hb and ferritin |
| Inflammatory arthritis | Your immune system attacks your joint lining | CRP and ESR, extended via your GP |
| Coeliac disease | Autoimmune reaction to gluten | Transglutaminase antibodies (IgA-tTG) |
| Vitamin D deficiency | A low vitamin D, more often in winter | 25-OH vitamin D |
| Vitamin B12 deficiency | Too little B12 for your nerves and blood production | Vitamin B12 |
Notice above all what is missing from that table: a row for fibromyalgia itself. It does not exist, and I think that empty space is the most honest thing on this page.
More on the thyroid is in thyroid symptoms in women. On a low iron, see anaemia in women. The gluten side sits in coeliac disease: symptoms, testing and gluten-free living.
What is the difference between fibromyalgia and rheumatoid arthritis?
Rheumatoid arthritis is inflammation, fibromyalgia is not. In rheumatoid arthritis your immune system attacks your joint lining, with swelling, warmth and often measurable inflammation values. In fibromyalgia your joints are not inflamed and CRP and ESR are usually simply normal, while you are genuinely in pain.
That difference also shapes how the complaint behaves. Rheumatoid arthritis gives swollen, warm knuckles and morning stiffness lasting over an hour. Fibromyalgia gives pain that wanders through your whole body, without visible swelling.
Take two women of 44, both with a CRP of 2 mg/l and an ESR of 9 mm/hour. Both perfectly normal. Yet that same number means something quite different for each of them.
The first has had pain wandering through her body for eight months and sleeps badly, while her joints are not swollen on examination. For her that normal CRP fits the picture exactly. Fibromyalgia does not produce inflammation, so the value rules nothing out and confirms nothing.
The second has visibly thick knuckles on both hands and is stiff for ninety minutes every morning. For her that same 2 mg/l is not reassuring at all, because in early rheumatoid arthritis CRP can stay normal while the joints are already inflamed. Her story weighs more than her result.
Same number, opposite meaning. This is why I am so wary of the sentence "my blood is normal, so there is nothing wrong". The number does not decide. The picture around it does.
The confusion is understandable, because in many women both start around the same age. How to recognise rheumatoid arthritis sits in rheumatoid arthritis symptoms in women. What CRP and ESR actually say is in what inflammation markers in your blood mean.
Researchers now understand fibromyalgia as pain amplification in your central nervous system, together with fatigue, memory problems, and sleep and mood disturbance (PMID 24737367). Your pain system is turned up. The pain is real, the cause just does not sit in the tissue that hurts.
What can you test yourself for chronic pain?
You can bring the look-alike conditions into view, and no more than that. Values like TSH, free T4, ferritin, Hb, CRP, ESR, vitamin D and vitamin B12 sit in an extended health checkup. They will not tell you whether you have fibromyalgia. They will tell you whether something else is playing a part.
That distinction matters enough that I would rather repeat it than let you read more into a result than it holds. These results confirm no fibromyalgia and rule none out. They can make the conversation with your GP more concrete, because some of the questions are already answered.
Gluten antibodies are not included here, by the way, that is a separate test. And rheumatoid factor and anti-CCP belong with your GP, because they only mean something once someone has actually examined your joints.
When do you take this to your GP?
See your GP if pain has sat across your whole body for more than three months, especially combined with fatigue and sleep that does not restore. Bring when it started, where the pain sits, and what has already been measured. That makes the conversation shorter and sharper.
What strikes me about women who carry this for years: they come in with a feeling and leave with a feeling. Come in with a timeline and a few results, and that conversation changes character.
On what happens when no cause is found, and which label you get then, read SOLK: what the diagnosis means. On why women's complaints are structurally recognised later, see the women's health gap: why symptoms are missed. And how to prepare such a conversation is in preparing for your GP appointment.
Thuisarts and the NHG stress with complaints like these that the clinical picture leads, never one value alone. There is no NHG standard for fibromyalgia; the GP leans on the standard for insufficiently explained physical symptoms. That too says something about where this field stands.
On what may help afterwards, Cochrane is cautiously positive: aerobic training probably improves quality of life, on moderate-quality evidence, and may slightly reduce pain (PMID 28636204). Whether that fits you is a conversation with your GP.
References
- Wolfe F, Smythe HA, Yunus MB, et al. The American College of Rheumatology 1990 Criteria for the Classification of Fibromyalgia. Arthritis Rheum. 1990;33(2):160-172. PMID 2306288.
- Wolfe F, Clauw DJ, Fitzcharles MA, et al. The American College of Rheumatology preliminary diagnostic criteria for fibromyalgia and measurement of symptom severity. Arthritis Care Res (Hoboken). 2010;62(5):600-610. PMID 20461783.
- Jones GT, Atzeni F, Beasley M, et al. The prevalence of fibromyalgia in the general population: a comparison of the American College of Rheumatology 1990, 2010, and modified 2010 classification criteria. Arthritis Rheumatol. 2015;67(2):568-575. PMID 25323744.
- Wolfe F, Clauw DJ, Fitzcharles MA, et al. 2016 Revisions to the 2010/2011 fibromyalgia diagnostic criteria. Semin Arthritis Rheum. 2016;46(3):319-329. PMID 27916278.
- Clauw DJ. Fibromyalgia: a clinical review. JAMA. 2014;311(15):1547-1555. PMID 24737367.
- Gendelman O, Amital H, Bar-On Y, et al. Time to diagnosis of fibromyalgia and factors associated with delayed diagnosis in primary care. Best Pract Res Clin Rheumatol. 2018;32(4):489-499. PMID 31174818.
- Bidonde J, Busch AJ, Schachter CL, et al. Aerobic exercise training for adults with fibromyalgia. Cochrane Database Syst Rev. 2017;6:CD012700. PMID 28636204.
- NHG and Thuisarts. Information on fibromyalgia and insufficiently explained physical symptoms. 2024. Available via thuisarts.nl.
Every blood test result at Lunara includes a professional assessment by a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
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