Have been feeling fatigued/ low energy and getting repeatedly ill. Had a blood test and vit d was 49nmol so classed as borderline low. Is this likely to be having an effect on my health? Most people discussing deficiencies on here are talking readings in the 20s. I know ferritin slightly below optimal can have a real effect but can’t find any data on borderline low vit d. Rest of blood results were ok - ferritin 36, b12 oddly 940 but dr said that wasn’t significant. Thanks all