Hey Maz,

Thanks for the kind words...  There's every reason to suspect a higher dose of vitamin D3 will push you past the tipping point for a pain free cluster headache response.

A 25(OH)D serum concentration above 100 ng/mL, (250 nmol/L in the UK), by itself is not an indication of vitamin D3 intoxication...  There are a number of vitamin D3 experts (endocrinologists) who say there's ample evidence 200 ng/mL, (500 nmol/L) is also quite safe.

The only real indication of vitamin D3 intoxication is a total calcium serum concentration above the normal reference range. 

Unless there's another comorbid condition involving the thyroid and/or parathyroid that results in too much parathyroid hormone (PTH), vitamin D3 intoxication is unlikely even at doses as high as 40,000 IU/day.  Our bodies make vitamin D3 so there are several built-in mechanisms in play that can limit its production and metabolism to prevent intoxication.

That said, it's always a good idea to keep your PCP in the loop.  Obtaining the 25(OH)D, PTH and calcium lab tests are also important until you reach a stable 25(OH)D serum concentration around 80 ng/mL, (200 nmol/L).  For most of us, that will require a vitamin D3 maintenance dose  of 10,000 IU/day.

Take care and please keep us posted.

V/R, Batch