Yes, HU messes with a lot of things in our bodies, but we take it because it’s lifesaving for us. As for the cramps, HU depletes magnesium in the body which was causing me to have cramps in my calves and feet. To counteract that, I use Liquid Magnesium, NOW brand, 1/2 t. daily in a little water. You can experiment with how much you need.
Another thing I’ll mention in case you start having a problem with it. I didn’t get mouth sores for a long time, but then started getting them, just one at a time. Chemo is known to cause mouth sores. Someone said they were using a zinc mouthwash which stopped the sores. I opted for a zinc lozenge, and no more sores when used once or twice daily. (I use Zand Lemon Zinc from Vitacost (online). HU messes with the mucous membranes throughout our bodies, in the sinuses, mouth, stomach, intestines, etc. I take certain supplements to help with nausea and vomiting from HU.

I have foot and leg cramps too and some pain in one toe. I have been told that toe joint is arthritic, but it flares from time to time. All this stuff is better for me after treatment. I think some issues are related to poor blood flow to feet and lower legs. I use massage to loosen the fascia in lower legs and keep feet and ankles mobile. I also do exercises with my feet to keep them mobile and reduce numbness. It is a battle. Best of luck to find a solution.