Relevant testing which may be considered can include:
As a first line, general pathology testing can be a goldmine of information (eg. iron studies, fasting blood glucose, blood lipids, ESR, hsCRP, general biochemistry, liver function test, Vitamin B12, folate, Vitamin D, hormonal panel, etc).
Functional Pathology, to list a few examples:
MTHFR gene testing/Methylation Profile
Omega-3 Index Test
Thyroid function testing (TSH, fT4, fT3, rT3, antibodies)