Dehydration and heart failure: what to know

Heart failure affects how effectively the heart moves blood around the body. Fluid loss from sweating, vomiting, diarrhoea, fever or medicines can contribute to dizziness, weakness and low blood pressure. At the same time, the heart may struggle with a sudden fluid load, causing breathlessness, cough or swollen ankles. These signs can overlap with other conditions, so neither thirst nor swelling alone tells you how much to drink. Your prescribed plan takes kidney function, medicines and congestion into account.

Follow the fluid and salt advice given by your heart-failure team rather than changing intake suddenly. If you have vomiting, diarrhoea, fever or heavy sweating, contact the team for specific instructions. Weighing yourself in the way your clinician taught you and recording breathlessness, swelling and urine changes can provide useful information. Do not stop diuretics or other heart medicines on your own; dehydration can alter how medicines affect you.

Call emergency services for severe breathlessness at rest, chest pain, fainting, blue lips, confusion or inability to stay awake. Seek prompt medical advice for rapidly worsening swelling, a new or worsening cough, palpitations, very little urine, repeated vomiting or dizziness when standing. A chronic disease review can help update your sick-day instructions before another illness occurs.

Ask for your personal fluid target, which medicines need review during vomiting or diarrhoea, and what change in breathing, weight or swelling should trigger a call.