Hi there Pastafool,

Yes, Michelle has the potassium about right. I believe the Eades (Protein Power) suggest 400mg/day at first, later lowering to 100mg.

The other thing you can do is switch to potassium salt - No Salt or Nu Salt. Much cheaper than the tablets! I just sprinkle it on my food instead of ordinary salt.
The pack will tell you how much potassium per teaspoon. I use a ¼ teaspoon measure so I have an idea how much I am getting.

Now you also asked about magnesium . Weakness in your legs suggests you also need mag. Magnesium is best taken in a 2:1 ratio with calcium. That's 2cal:1mag. You should be aiming at 1000mg cal and 500mg mag. A total of 600mg mag (including your multivite) is fine.

All the best to you, matey.

Rosebud