A few medical tests can be helpful for those suffering with chronic pain:
C-Reactive Protein (CRP): this looks for chronic inflammation, which may indicate an underlying medical disorder.
Arthritis Panel: If significant inflammatory joint pain is the issue--RF (rheumatoid factor) and ANA (anti-nuclear antigen).
Thyroid function, as abnormal levels can exacerbate pain: TSH, free T3, free T4.
25-hydroxy vitamin D, as low levels can cause pain (supplementation can help with pain).