Fibromyalgia and overlapping conditions

Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (ME/CFS) shares several features with fibromyalgia — fatigue, unrefreshing sleep, cognitive difficulties, and widespread pain. A significant proportion of people meet the diagnostic criteria for both conditions.

The defining difference is post-exertional malaise (PEM) — a delayed, disproportionate worsening of symptoms after activity. Fibromyalgia flares do not follow the same pattern.

If you have fibromyalgia and suspect you also have ME/CFS, the key signal to watch for is whether activity reliably causes a significant symptom crash 12 to 72 hours later. For more on the distinction, see our FAQs or our ME/CFS section.

IBS is a common digestive condition involving abdominal pain, bloating, and disrupted bowel habits. It is one of the most frequently reported conditions alongside fibromyalgia — research consistently finds that a substantial proportion of people with fibromyalgia also have IBS, and that people with IBS are meaningfully more likely to develop fibromyalgia.

Both conditions involve changes in how the nervous system processes pain and sensory input. Managing them together usually means working with your GP on diet, stress management, and medication — and recognising that flares in one often coincide with flares in the other.

Migraine is more common among people with fibromyalgia than in the general population. Early research found close to half of people with fibromyalgia also experienced migraine, and larger population studies have since confirmed a consistent association.

The two conditions share features of altered sensory and pain processing. If you experience severe, recurrent headaches — particularly with visual disturbance, nausea, or sensitivity to light and sound — it is worth raising with your GP rather than assuming the headaches are simply part of your fibromyalgia.

POTS is a form of orthostatic intolerance — a condition in which symptoms worsen on standing, often including dizziness, racing heart, nausea, and cognitive fog. It is more commonly associated with ME/CFS than with fibromyalgia, but the overlap with fibromyalgia is well established and likely underrecognised.

If you find that standing up triggers dizziness or a significantly raised heart rate, or that your symptoms improve noticeably when lying flat, it is worth discussing an assessment with your GP.

Interstitial cystitis, also called bladder pain syndrome, causes chronic pelvic pain, urgency, and frequent urination. It is significantly more common in people with fibromyalgia than in the general population, though still less common overall than IBS or migraine.

If you have persistent pelvic pain, a frequent need to urinate, or bladder symptoms without signs of infection, a GP referral to a urologist may be appropriate.

TMD affects the jaw joint and the surrounding muscles, causing pain, clicking, or restricted movement. It commonly co-occurs with fibromyalgia, and the severity of one tends to track with the severity of the other.

Dentists and specialist jaw physiotherapists can help with TMD directly. The general principles of fibromyalgia management — reducing muscle tension, managing stress, and treating pain — also apply.

Depression and anxiety are more common among people with fibromyalgia than in the general population. This is not evidence that fibromyalgia is a psychological condition. It reflects the genuine weight of living with constant pain, disrupted sleep, and reduced function — all of which would raise the risk of depression or anxiety in anyone.

Mental health support — whether from a GP, a therapist experienced in chronic illness, or peer support — is a legitimate part of fibromyalgia care, not a sign that the underlying illness is ‘really’ psychological.

Restless legs syndrome causes an uncomfortable urge to move the legs, particularly at night. It is more commonly reported by people with fibromyalgia than by the general population, and it can worsen the sleep disruption that is already a core feature of fibromyalgia.

Treatment for restless legs — including iron supplementation where levels are low, and specific medications — is worth discussing with your GP if symptoms are affecting sleep.

Some researchers group fibromyalgia, IBS, migraine, TMD, and several of the other conditions on this page under the label ‘central sensitivity syndromes’. The idea is that they share a common underlying mechanism — an overactive central nervous system response to pain and sensory input.

The framing is useful for understanding why these conditions so often travel together. It is also contested. Some researchers argue that grouping distinct conditions under a single label risks oversimplifying them and may affect how they are treated.

For patients, the practical point is this: if you have one of these conditions, you are more likely to have another. Watching for the signs — and raising them with your GP — is more important than the clinical label used to group them.

If you already have a fibromyalgia diagnosis, new or distinct symptoms are sometimes assumed to be part of the same condition. That assumption is not always correct. IBS, migraine, POTS, interstitial cystitis, and TMD all have their own diagnostic processes and their own specialists.

If symptoms are persistent, affecting your daily life, or do not fit your usual fibromyalgia pattern, it is reasonable to ask for a specific assessment. A fibromyalgia diagnosis does not close the door on other diagnoses — and managing each condition on its own terms tends to work better than treating everything as one undifferentiated illness.