Using patients who were referred to a subspecialty pain medicine clinic to be treated for widespread muscular/connective tissue pain, and then separating people who met the criteria for fibromyalgia into smaller groups by age, a small experiment (n=23) found that patients with medication that targeted insulin resistance, metformin, reported less pain. 

Fibromyalgia is a blanket term for chronic pain not caused by a disease such as cancer or a medical event. The global economic impact of fibromyalgia is estimated to be enormous, the way all estimates are because they use virtual money - $100 billion each year is commonly thrown around. It's hard to know because though fibromyalgia has been extensively studied, there are no evidence-based diagnostics or therapies, other than pain-reducing drugs.

Perhaps that may change. After separating patients who met accepted criteria for fibromyalgia from normal individuals using a common blood test for insulin resistance, they treated the fibromyalgia patients with a medication targeting insulin resistance, which dramatically reduced their pain levels.

HbA1c in patients with fibromyalgia versus controls.

When compared with age-matched controls, the A1c levels of the fibromyalgia patients were significantly higher. Insulin insulin causes dysfunction within the brain's small blood vessels and reports are that this also present in fibromyalgia. The confounder is that the authors used the A1c level for an American term called pre-diabetes, not diabetes, which has no clinical relevance and isn't accepted in the rest of the world. It isn't going to bring comfort to fibromyalgia patients that they are already greeted with skepticism and now are going to be lumped in with a dubious diagnosis like pre-diabetes. Especially when it's a tiny retrospective cross-sectional study where both insulin resistance and fibromyalgia were simultaneously assessed. Since patients with fibromyalgia are commonly overweight or even obese it could be that the strain of processing so many calories led to insulin resistance, and not that insulin resistance is linked to fibromyalgia.

Citation: Pappolla MA, Manchikanti L, Andersen CR, Greig NH, Ahmed F, Fang X, et al. (2019) Is insulin resistance the cause of fibromyalgia? A preliminary report. PLoS ONE 14(5): e0216079. DOI:10.1371/journal.pone.0216079