Blood sugar levels fluctuation.

My mother is a breast cancer patient, she had gone through by 5 chemo till now, 4 chemo wr same, this time the chemo is chngd to dacctaxel and carboplatin bfre chemo she hd been injected wid dexamethasone & avil injection one nyt bfr hr chemo & next dy mrng before chemo, some medicine to tk after chemo dexa 4mg BD, emset 8mg TDS, Iron, calcium ,folic acid, probiotics,etc after dat hr sugar shoot up to 290/415 on Sunday mrng & 327 in evening, then on Monday mrng it was 334 we took her to hospital (cancer hospital n cardiologist for regular medicine), cardiologist advised to double the dose of Metformin from 500mg to 1000mg BD rest will be same, and in cancer hospital dey said due to dexa it goes up so will stop this, then we took 1000mg at night then on Tuesday mrng her sugar lower down to 55 we skipped her mrng medicine, then at afternoon it ws 175, she tk hr night sugar medicine, today mrng it ws 84 we skipped mrng medicine, she felt very low, heavy head, fatigue, plzz advice somethin