Vitamin Blood test

[clatow23]

Hi guys, so I have my vitamin results back after being advised those with an underactive thyroid should get them tested

Serum Folate 3.5 ng/ml [> 3.9]

Serum Vitamin B12 540 ng/l [197-771]

Vitamin D 16 nmol/L [> 51]

They want to repeat the Folate test, but the vitamin D even though it's low says abnormal but expected, no further action

Am I correct though that they are supposed to treat Vitamin D under 25, nmol/L which mine is?