@Mimi
One strategy that may help to reduce your BH4 requirements, and therefore possibly lower the daily BH4 dose that you need, is taking antioxidants and supplements to reduce peroxynitrite alongside your BH4 pills.
BH4 is very sensitive to oxidative stress, and is very quickly oxidized to BH2 by reactive oxygen species, and by peroxynitrite. In fact, if you have high levels of oxidative stress in your body (and studies show ME/CFS patients do), much of the BH4, which is an antioxidant itself, may just end up as a sacrificial antioxidant target for these reactive oxygen species in your body — and a very expensive antioxidant target at that!
So if you were to take an array of antioxidants with your BH4, and also some peroxynitrite scavengers, this may protect the BH4 you take from oxidation, and thus make this BH4 go further, so that you could then take less, and save money.
I am not sure what the best antioxidants are for this purpose, perhaps you can research it; but
this study noted that:
it has recently been shown that ascorbate increases tetrahydrobiopterin levels in cultured endothelial cells by preventing its oxidation
And
this study found that a regimen of L-arginine, vitamin C, and vitamin E increased BH4 levels by 32%.
A good list of peroxynitrite scavengers can be found in
this post.
