My Husband Has High Blood Pressure. He Is On Medication

My husband has high blood pressure. He is on medication (Lisinopril and HCTZ) and a low sodium (somewhat diet). His blood pressure has gone up lately. He started taking magnesium supplement at Christmas. Could that cause his blood pressure to go up? When we discovered it, he was at 190 over 120. We got it down to 135 over 105. He is now up to the 160s/70s over in between 94 and 97