Hello dear. Welcome to HealthCareMagic. Thanks for trusting us. I have gone through your questions and understood your query. Diltiazem is calcium channel blocker used to treat hypertension, chest pain, and certain heart rhythm disorder. Common side effects are dizziness, weakness, headache, nausea, rash, lightheadedness, edema/swelling, nausea and vomiting, muscle pain etc. If any of these - like extreme exhaustion - you feel really hard and bother your quality of life, please contact your treating doctor. Using diltiazem and calcium derivative supplement may have interaction, which may decrease the effect of diltiazem in the body. But diltiazem and magnesium have no interaction. You should tell your doctor about another drugs you consume along with diltiazem, to consider the effect, interactions, benefit and dosage needed. To be concerned, do not stop using diltiazem suddenly, it may cause your condition worse. Do not lower or increase the dose without your doctor s permission. Use diltiazem regularly to get most benefit, and please check your blood pressure often. I hope these can be helpful to resolve your problems. If there s anything else you need to discuss, please let me know and I d be glad to help you. Wish you get better soon. Take care. Regards, dr. Asti Yuliadha