Fibromyalgia — why does the whole body hurt, even when tests don’t show the cause?

When your body hurts, but test results don’t explain why

Imagine waking up in the morning after eight hours of sleep and still feeling as if you hadn’t rested for a single moment. Your back, neck, shoulders and legs ache. The touch of clothing can be unpleasant, ordinary duties are exhausting, and focusing on a simple task takes far more effort than it used to.

You have tests done and visit one specialist after another, but you don’t get an answer that would explain all your symptoms.

This is what everyday life can look like for a person with fibromyalgia — a chronic pain syndrome that is often accompanied by fatigue, sleep disturbances, difficulty concentrating and increased sensitivity to stimuli.

One of the greatest challenges of this condition is that its symptoms usually cannot be explained by damage to a single muscle, joint or other structure. Routine laboratory tests may show no characteristic abnormalities, yet the symptoms are real and can significantly limit daily functioning.

To better understand fibromyalgia, it is worth looking at how the nervous system receives, processes and regulates pain signals.

1. Fibromyalgia — what is happening in the nervous system?

Pain is an essential protective mechanism. It alerts us to a potential threat and helps us avoid further damage. However, it is not a simple readout of a signal sent by the tissues. How we experience it also depends on the way the brain and spinal cord process information.

In some people with fibromyalgia, this regulatory system works differently than in people without this pain syndrome.

Central sensitization — when the nervous system becomes hypersensitive

One of the mechanisms studied in fibromyalgia is so-called central sensitization, i.e. increased reactivity of the structures of the central nervous system to sensory stimuli, including pain stimuli.

In practice, this may mean that a stimulus that causes slight discomfort in one person causes a much stronger sensation of pain in another.

Some people feel pain from a light touch, the pressure of clothing or gentle pressure. The phenomenon in which a normally non-painful stimulus causes pain is called allodynia. Hyperalgesia, in turn, means an excessively strong pain response to a stimulus that is normally painful as well.

It can be compared to an alarm that goes off at a much smaller stimulus than before.

This does not mean, however, that the brain “makes up” the pain. It means that the very process by which pain arises and is regulated is more complex than it might seem.

It is worth being precise here: central sensitization is an important model explaining some of the symptoms of fibromyalgia, but it is not the only mechanism, and its presence cannot be unambiguously confirmed by a single routine test.

Does the brain of a person with fibromyalgia work differently?

Neuroimaging studies and experiments assessing pain sensitivity point to differences in the processing of stimuli and in pain-inhibition mechanisms in some people with fibromyalgia.

This does not mean, however, that there is one characteristic brain picture that makes it possible to diagnose the condition from an MRI scan.

Current knowledge suggests that fibromyalgia is a syndrome with a varied background. Both central mechanisms and signals coming from peripheral tissues, regulation of the nervous system, sleep and individual biological susceptibility may play a role.

These factors do not play the same role in every person.

2. Why are fatigue, sleep problems and brain fog associated with fibromyalgia?

Fibromyalgia is not limited to pain. For many people, a lack of energy, difficulty thinking and a sense that the body is not recovering as it should are just as hard to bear.

Sleep that doesn’t bring rest

People with fibromyalgia often report that they sleep long enough but wake up tired. They may have trouble falling asleep, wake up frequently, or experience sleep as shallow and not very restorative.

The relationship between sleep and pain works both ways. Pain makes it harder to fall asleep and worsens sleep continuity, while insufficiently restorative sleep can increase sensitivity to pain, fatigue and difficulty concentrating.

As a result, a vicious circle can form: pain worsens sleep, and worse sleep makes it harder to cope with pain.

This does not mean that every person with fibromyalgia has identical disturbances in sleep architecture, or that the condition can be reduced to a deficiency of one sleep phase or one hormone.

Brain fog — when it’s hard to gather your thoughts

Some people describe difficulty concentrating, recalling words, remembering information or doing several things at once. This experience is sometimes called brain fog.

Such symptoms may be related to many overlapping factors, including pain, sleep disturbances, fatigue and cognitive load. Their severity may change from day to day.

Not all memory problems should automatically be attributed to fibromyalgia. If they are new, worsen quickly or clearly change daily functioning, they require medical assessment.

Stress — an important factor, but not the only explanation

Long-term stress can affect sleep, muscle tension, the functioning of the autonomic nervous system and the way pain is experienced. In some people it may be one of the factors that intensify symptoms.

It does not follow, however, that fibromyalgia is a condition caused solely by stress, or that it can be cured by relaxation alone.

As with other chronic complaints, what matters are the interdependencies between biological processes, daily functioning and an individual health history.

3. Does fibromyalgia have a single cause?

There is currently no evidence that all cases of fibromyalgia have one common source that can be detected and removed.

In different people, symptoms may appear in different circumstances. Some link their onset to an infection, an injury, a period of heavy physical and psychological strain, or a deterioration in sleep. In others, symptoms develop gradually, without any clear preceding event.

Studies point to the involvement of many factors, but their exact role in the development and persistence of the condition is not yet fully understood.

Injury and chronic pain

An injury can lead to persistent pain, reduced activity and changes in the way stimuli are processed. In some people, chronic pain after an injury may coexist with generalized hypersensitivity.

Infections and other health problems

In some patients, symptoms begin after an infection. Fibromyalgia can also coexist with other conditions, including rheumatic diseases. A temporal relationship, however, does not prove that the infection is still actively causing the symptoms. Similarly, the mere occurrence of complaints after exposure to mold or chemical substances does not confirm that they are the cause of fibromyalgia.

Hormones and the menopausal period

Hormonal changes can affect sleep, mood, energy and the experience of pain. The perimenopausal period may therefore be an important clinical context for some women.

Gut, diet and food sensitivities

Gastrointestinal symptoms often coexist with fibromyalgia. It is worth assessing them, especially if complaints suggesting another condition appear, for example coeliac disease or irritable bowel syndrome.

4. How is fibromyalgia diagnosed?

Fibromyalgia is diagnosed on the basis of the clinical picture, medical history and assessment of symptoms. There is no single blood test, inflammatory marker or imaging study that would confirm the condition on its own.

Current diagnostic criteria take into account primarily:

• the widespread nature of pain complaints
• the duration of symptoms — usually at least three months
• the severity of fatigue
• sleep quality and feeling rested after waking
• cognitive difficulties and other accompanying symptoms

The examination of 18 specific tender points also plays a major role; at least 11 of them are typically painful on pressure.

Importantly, fibromyalgia can coexist with other diseases. Diagnosing it therefore does not mean that other possible causes of symptoms should be ignored. A doctor may order appropriate tests, depending on the patient’s history and clinical picture, to assess, among other things, thyroid disease, inflammatory conditions, anaemia or other disorders producing similar symptoms.

Not everyone needs a broad set of tests. The scope of diagnostics should result from specific grounds.

5. What can help a person with fibromyalgia?

There is no single method that effectively helps everyone with fibromyalgia. The goal of management is to reduce pain and fatigue, improve sleep and regain the best possible everyday functioning.

Most often, the best results come from an individually tailored, multi-directional approach.

Gradually adjusted activity

Movement can support physical fitness, well-being and the functioning of people with fibromyalgia. In the EULAR recommendations, exercise is among the non-pharmacological interventions with the strongest support. This is not about forcing yourself into intense workouts despite severe symptoms. Activity should be adjusted to current abilities and increased gradually, taking into account the body’s response.

For people who additionally experience post-exertional worsening of symptoms, choosing activity requires particular caution and individual assessment.

Improving sleep quality

It is worth looking at sleep regularity, resting conditions, pain that makes it hard to fall asleep, and any sleep disorders that require separate diagnosis.

Psychological support

Chronic pain can affect mood, relationships, the sense of safety and the ability to cope with everyday duties. Psychotherapy, including cognitive behavioural therapy, can help some people cope better with pain, stress and limitations.

Individual assessment of other health problems

If, besides pain, there are symptoms suggesting another condition, it is worth having them properly diagnosed. This applies, among others, to hormonal disorders, inflammatory diseases, neurological problems and sleep disorders.

There is no need to run every possible test or to search at all costs for one hidden cause. What matters is identifying problems that could genuinely change the course of management.

6. What about FSM microcurrent therapy?

FSM, or Frequency Specific Microcurrent, is a method that uses low-intensity microcurrents applied with specific frequency parameters.

In practice, a session may involve applying electrodes or moistened compresses to selected areas of the body. The details of the procedure depend on the individual situation and the protocol used.

FSM is one of the methods that are sometimes considered as a complement to work with people experiencing chronic pain. Research on FSM includes, among others, clinical studies on chronic pain. There are also publications devoted to other uses of microcurrents, but results concerning one technology, protocol or patient group cannot automatically be transferred to all microcurrent methods.

At HoliVibe, we treat FSM frequencies as a complementary method, not one that replaces medical diagnostics, rehabilitation or other justified forms of treatment. Potential benefits should be assessed individually, without assuming a specific result in advance.

7. Is it possible to function with fibromyalgia?

Fibromyalgia can have a chronic and variable course, but this does not mean that the severity of symptoms must stay the same throughout life.

Some people manage to achieve significant improvement — reducing pain, sleeping better, increasing their tolerance of daily activities and regaining greater independence. In others, symptoms remain more persistent and require long-term, multi-directional support.

No specific outcome can be promised, nor can any single pain threshold be named beyond which the body will certainly return to balance. There is also no confirmed rule that keeping pain below a certain value for four months leads to a cure of fibromyalgia. It is, however, worth observing what really helps.

Sometimes improvement does not begin with one breakthrough solution, but with a combination of several well-chosen actions.

In conclusion

Fibromyalgia is a complex pain syndrome whose mechanisms are still being studied. We know more and more about altered pain processing, the importance of sleep and the interdependencies between symptoms. Still, we are unable to explain all cases with a single mechanism or to point to one method that works for everyone.

That is why an individual approach, reliable diagnostics and drawing on a variety of forms of support are so important.

If you are struggling with chronic pain, you don’t have to choose between ignoring your symptoms and searching for one miraculous cause. You can gradually get to know your body, use the forms of help available and look for the kind of management that genuinely improves your quality of life.

Scientific sources and further reading

• 1.
  Wolfe F. et al. (2016), 2016 Revisions to the 2010/2011 Fibromyalgia Diagnostic Criteria. PubMed — ACR diagnostic criteria.
• 2.
  Macfarlane G.J. et al. (2017), EULAR revised recommendations for the management of fibromyalgia. Annals of the Rheumatic Diseases.
• 3.
  Smeets Y. et al. (2024), Role of non-invasive objective markers for the rehabilitative diagnosis of central sensitization in patients with fibromyalgia: A systematic review. PubMed.
• 4.
  Fibromyalgia: A Review of the Pathophysiological Mechanisms and Multidisciplinary Treatment Strategies (2024). PubMed.
• 5.
  Gregory W.M. et al. (2025), Frequency-specific microcurrent improves hand function and Raynaud's symptoms in scleroderma: results of two pilot studies. PubMed.