Hi I know it's that time of year when Vit D goes low, I've had prescription loading dose every year for last 4 years if 40.000iug a week for seven weeks. This time GP refused my repeat prescription request and asked for blood test. Vit D came back 34.2 and calcium was 2.25. My mum has severe osteoporosis so am worried about getting this. I'm also surprised why D so low considering have high annual dose and take D3 every day too. Does anybody know why D can drop so low even when supplementing. I know it affects thyroid function in winter too.