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High Blood Pressure

Corrections for low sodium levels

06/07/2007

Question:

I have been taking a diuretic to manage high blood pressure, as well as eating a reasonably low-salt diet (pretty close to DASH). This has worked out fairly successfully. However, in a recent blood test my sodium level was 129, where I understand the lower end of normal is about 135. Other blood indicators are normal.

What steps if any should I take to bring my sodium up to desired levels? Would this involve increasing sodium intake (not eating a diet as low in sodium); or cutting back on the diuretic (since I think this is supposed to expel sodium); or both; or something else? Thanks for your guidance.

Answer:

A low serum sodium level (hyponatremia) is a relatively common side effect of diuretic therapy.  If it is mild, it is harmless, but if it becomes more severe, it can be dangerous or even deadly.

The development of hyponatremia has nothing to do with salt intake.  Diuretics interfere with the kidneys' ability to regulate water and salt output.  Diuretics increase the excretion of salt and water, but make it harder for the kidney to get rid of water without salt.  If one drinks more water than usual, it can "dilute" the body, leading to hyponatremia.  In your case, reducing the intake of free water (soft drinks, coffee, tea, beer) would probably fix the problem.

Some patient are very sensitive to this effect of diuretics and can become severely hypopnatremic.  In that case, it is best to switch to other types of blood pressure medication.

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Response by:

Max C Reif, MD Max C Reif, MD
Professor of Medicine
Director of Hypertension Section
College of Medicine
University of Cincinnati