In Stages 4‒5 of CKD, or when your eGFR is under 35, high doses of magnesium should be avoided. When kidney functionality is low, there is a risk that your magnesium levels may become too high. Sodium bicarbonate taken orally is an effective alternative to magnesium as an alkalizing agent. Studies show that bicarbonate therapy slows the decline in kidney function in more advanced CKD and in the presence of metabolic acidosis.