Wow, my Vit D is low
Despite taking 4,000 to 8,000 units per day for the past few months.
National Institute for Health and Care Excellence
NICE
Do not routinely test for vitamin D deficiency in people who are asymptomatic.
https://www.youtube.com/@Campbellteaching
https://drjohncampbell.co.uk
https://www.patreon.com/JohnCampbell2
Since Vitamin D has numerous forms. It seems to me that the effectiveness of Vitamin D would depend on the balance of the forms. I am leaning toward the idea that a few minutes of sun at noon is the best way to get vitamin D.
Apparently free fructose can decrease vitamin d levels. This is found in HFCS, Agave Nectar and invert sugar. There are various ways to separate sucrose into glucose and fructose. My guess is that if you ate something that destroys vitamin D, that the test would show that.
Not surprising considering your age and climate in the UK.