Version July 2025
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What is the syndrome of inappropriate antidiuretic hormone secretion (SIADH)? —
This is a condition that happens when the body makes too much antidiuretic hormone ("ADH"). ADH helps manage the amount of water in the body. If you have too much ADH, your kidneys can't get rid of water. Fluid builds up in your body and dilutes the amount of salt in your blood. This causes a condition called "hyponatremia."
What causes SIADH? —
Many things can cause SIADH, including:
●Medicines – These include certain medicines used to treat type 2 diabetes, high blood pressure, seizures, and cancer.
●Infections such as pneumonia
●Surgery
●Brain and spinal cord problems – This includes strokes, bleeding, or an infection in the brain.
●Cancer – This includes different types of lung cancer (especially small cell) and cancer of the stomach, pancreas, or brain.
What are the symptoms of SIADH? —
The symptoms are the same as the symptoms of hyponatremia, which include:
●Nausea and vomiting
●Headache
●Confusion or trouble thinking clearly
●Feeling weak or tired
●Feeling restless or irritable
●Muscle weakness, spasms, or cramps
●Seizures or passing out
Is there a test for SIADH? —
Yes. Tests include blood and urine tests.
How is SIADH treated? —
It depends on what is causing your SIADH. For example, if you have an infection, your doctor might prescribe medicines to treat it. They might also tell you to:
●Limit how much fluid you drink.
●Eat salt tablets, or get a saltwater solution into a vein.
●Stop taking the medicine that is causing the problem.
Patient education: Hyponatremia (The Basics)
Patient education: Fluid restriction (The Basics)
