CHF and low blood pressure: what should you know?

Congestive heart failure changes how the heart fills or pushes blood forward. Low blood pressure may then cause light-headedness, weakness, blurred vision, nausea, or fainting. It can also appear after a dose change, dehydration, vomiting, diarrhoea, infection, or another heart problem. The reading itself matters less than the symptoms, the trend, and how you feel when standing.

Do not assume that every dizzy spell is caused by CHF. Dizziness has many possible explanations, including inner-ear problems and medication effects. Read more about [Dizziness](/symptoms/dizziness/).

Sit or lie down when symptoms begin, rise slowly, and avoid driving while faint or unsteady. Take prescribed heart medicines exactly as directed; do not stop a diuretic, blood-pressure medicine, or other treatment without advice. Keep a record of readings, symptoms, medicine timing, fluid intake, and recent illness. Contact a clinician promptly if symptoms recur or follow a new prescription. A [GP Consultation](/treatments/consultations-and-assessment/gp-consultation/) can help review medicines and look for dehydration, rhythm changes, or worsening heart function.

Seek emergency help for fainting, confusion, severe weakness, new chest pressure, blue or grey lips, severe breathlessness, or cold and clammy skin. Get urgent medical advice for repeated near-fainting, a rapid or irregular heartbeat with dizziness, or a marked change from your usual readings. These symptoms can signal that the circulation is not keeping up with the body's needs.

Ask which blood-pressure readings are concerning for you, whether any medicine or recent illness could explain the change, how much fluid is appropriate for your heart condition, and what to do after vomiting, diarrhoea, or a missed dose.