My 8 year old has achey joints, headaches, emotional swings, feeling cold and on and off constipation. her ferritin is 27 ug/l, saturation 44%, haemoglobin 128 g/l and red cell folate (folic acid) is 1918 nmol/l ?

Hypothyroidism?: The labs that you report are normal. The symptoms are not normal. The symptoms are somewhat suggestive of hypothyroidism. I would recommend addressing the symptoms with your child's pediatrician.

More info needed: I hope your physician is seeing your child to establish a diagnosis and a plan to treat. Has your child had fevers or weight loss? Any family history of thyroid disease?