@colleenyoung Yes, I was prescribed 20 micrograms vitamin D per day, double the recommended dose for every adult during the dark winter months here in Sweden. I will do a follow up test in six months to check for any changes. However since then I found out that not only MPN but also HU affects the bodys ability to absorb vitamins such as vitamin D. If so, low levels of vitamin D ought to be a common problem among those of us with ET and on HU?