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Normally anti hypertensive medication
is effective when taken in the early morning.I mean to say , the daytime control is good.
Her BP might be fluctuating due to poor control.She may need a change of drug or change in dosage.
Along with medication , diet control should be strict.Avoid salt intake , avoid high fat diet . She should practice yoga
(if feasible) or meditation
daily for 35 - 45 minutes.This helps in reducing stress
and reducing BP.
Hope this information helps you.If you need more information feel free to mail me.