CONDITION
Insulinoma
Insulinoma is a tumour of the pancreas that produces excessive insulin, the hormone that lowers blood glucose. In dogs, these tumours are nearly always malignant, and metastatic spread to lymph nodes or liver is common at the time of diagnosis. The excess insulin causes episodes of low blood sugar, which can affect the brain and nervous system. Owners often notice intermittent signs: sudden weakness, confusion, wobbliness, trembling, or collapse that resolve on their own or after eating. The pattern tends to be episodic because insulin is released in bursts, not continuously. Signs may occur hours after a meal, during exercise, or with no obvious trigger. This page explores what low blood sugar can look like in day-to-day life, how the diagnosis is made, the role of imaging in understanding spread, and the approaches available—including surgery, dietary strategies, and medication—alongside what each may and may not achieve.
Why this matters now
Insulinoma in dogs tends to appear in middle-aged to older animals, with most cases diagnosed between eight and twelve years of age. Certain larger breeds, including Golden Retrievers, Boxers, and Irish Setters, appear over-represented in case series, though the condition can occur in any breed or mixed-breed dog. In cats the condition is rare enough that age and breed patterns are less clear. There are no known dietary, environmental, or lifestyle triggers; the condition arises from spontaneous changes in the insulin-secreting cells of the pancreas.
Most canine insulinomas are malignant, and metastatic spread to the liver, lymph nodes, or other abdominal sites is already present in roughly half of dogs at the time of diagnosis. Despite this, clinical signs are often episodic and intermittent, because insulin release from the tumour occurs in bursts rather than continuously. Between episodes the dog may appear entirely normal, and weeks or months can pass before the pattern becomes clear enough to prompt investigation. Over time, episodes may become more frequent or more pronounced as the tumour burden increases.
Signals & patterns
Early signals
Intermittent weakness or lethargy
The dog may seem unusually tired or reluctant to move for a period of minutes to hours, then recover completely. These episodes often follow exercise or a gap between meals, when glucose demands are higher or stores are lower.
Brief confusion or disorientation
An owner may notice the dog appearing vague, staring into space, or failing to respond to familiar cues. The episode typically resolves on its own, and the dog returns to normal behaviour without intervention.
Wobbliness or unsteady gait
The dog may walk as though slightly drunk, with hind limbs crossing or front legs splaying. This can be subtle and mistaken for joint stiffness or fatigue, particularly in older animals.
Increased appetite or food-seeking
Some dogs become noticeably hungrier or more persistent about scavenging, which may reflect the body's attempt to correct low glucose. This sign is non-specific and easily attributed to other causes.
Later signals
Collapse or loss of consciousness
The dog may suddenly fall or become unresponsive, sometimes with muscle twitching or paddling movements that resemble a seizure. These episodes are typically short-lived, and the dog may recover within minutes, though confusion can linger.
True seizures
In some cases, low glucose triggers generalised seizure activity with loss of consciousness, muscle rigidity, and paddling. Distinguishing these from other causes of seizures requires measurement of glucose at the time of the event, which is rarely possible at home.
Weight gain despite no change in feeding
Chronic excess insulin can promote fat storage, and some dogs gain weight even when their diet remains constant. This is a less common sign and can be overlooked if the dog is otherwise behaving normally between episodes.
Click to read about the biological mechanisms
How this is usually investigated
Options & trade-offs
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