Brief Answer: Refer below Detailed Answer: Hi, Thanks for consulting HealthcareMagic! Magnesium oxide is used for treating acid indigestion, heartburn and low magnesium levels in the body. It also may be used for other conditions as determined by your doctor. Magnesium oxide is an essential mineral. It works by adding magnesium to your body if your magnesium levels are low. As an antacid, it works by neutralizing stomach acid. B2- Vitamin is a supplement. Your doctor based on physical examination and your medical history could have suspected any of the indications to use these medications. There is no specific rule that a blood test should be done before initiating these. However, I cannot surely say without doing a physical, whether you really required these drugs and can be initiated safely or not. And no one can be sure that whether one can be allergic to these things until at least a dose of medication is taken (if u develop any allergic symptoms like ash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue, black, tarry stools; nausea; slow reflexes; vomit that looks like coffee grounds) However, these kind of allergies are very very very rare. No test will usually be done to check whether you are allergic to these kind of drugs. Hope I have answered your query. If you are satisfied, you may now close the discussion and rate the answer. If you like my answers and wish me to answer in future, bring it to my attention: Dr Vasanth. Url link is as follows: WWW.WWWW.WW Wish you good health!

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