For other owners

Insulinoma in dogs

Honest reality instead of a heroic tale. Not "do exactly the same and your dog will live longer" — but: this is how it went with optimal care, and this is how you need to adapt it realistically to your situation.

In hindsight

A different truth about Pebbels' illness

For over nine months we fought against what we had been told was an insulinoma. The symptoms, the readings and the response to treatment all fit that diagnosis. Only after Pebbels' death, looking back with all the records and findings in hand, did we understand: the truth was probably a different one.

In January 2024, Pebbels had a mammary tumour removed — a ductal carcinoma with an aggressive classification (grade II, high mitotic rate). At the time we were told: completely removed. What no one told us: with this histology, the probability of it later returning as metastases is 25 to 50 percent — despite a clean resection. Close follow-up monitoring would have been the standard. It was never recommended to us.

19 months later came the hypoglycaemia crises. The diagnosis "insulinoma" was made — functionally consistent, but never confirmed by a tissue sample. No tumour was ever located. What the later CT scan in April 2026 showed — multiple lesions in the liver, spleen and lungs — fits a metastatic mammary carcinoma far better than a pure insulinoma.

We cannot prove it — no autopsy was carried out. But all the available findings point to it: Pebbels' actual illness was probably not a new tumour that arose in 2025. It was the breast cancer from 2024, which had spread over time and in the end developed an insulin-active component.

Importantly — this changes nothing about the treatment. And that is exactly why everything we pass on this page remains valid. In both cases the underlying problem is the same: tumour cells that release insulin uncontrollably and make the blood sugar crash. The management is therefore identical too — continuous glucose monitoring (CGM), demand-led diazoxide, smart feeding and fast action in an emergency. Whether a primary insulinoma or insulin-producing metastases: for everyday life with the dog, and for the monitoring, medication and emergency experiences here, it makes no difference.

So this realisation changes nothing about our loss and nothing about the treatment — but it adds a message we very much want to give to other owners: after breast cancer surgery, stay vigilant.

Note: This is our most likely reconstruction in hindsight — a working hypothesis, not a proven diagnosis and not veterinary advice. It explains why the insulinoma content below stays valuable for owners with a genuine insulinoma — but in Pebbels' own case was probably the wrong box to tick. What we want to give to owners after breast cancer surgery is further down.

First, understand it

What exactly is an insulinoma?

An insulinoma is a tumour in the pancreas — on the so-called beta cells, which normally regulate blood glucose. This tumour releases insulin uncontrollably. Insulin pulls glucose out of the blood into the cells — too much of it, and blood glucose crashes. This hypoglycemia causes the trembling, the weakness, the disorientation, even seizures.

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Almost always malignant

In dogs the insulinoma is malignant in over 95 % of cases — unlike in humans, where it is usually benign. So it is not a "harmless lump" but a spreading tumour.

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It forms metastases

Around half of all dogs already have visible secondary tumours at diagnosis — most often in the liver and lymph nodes. In nearly all of the rest, they develop over the course of the disease.

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Not curable

Even after surgery the hypoglycemia almost always returns, because metastases or regrowing tissue keep producing insulin. Every treatment buys time — not a cure.

It is classified into three stages: I (only in the pancreas), II (lymph nodes affected), III (distant metastases, often the liver). The figures come from the current specialist literature — more under Studies & Sources.

Our experience

What we learned

Six things that made the biggest difference in daily life with the insulinoma.

01

Dose to need

Don't give diazoxide by a blanket maximum dose, but according to real values — ideally CGM-based, adjusted daily. Cortisone (prednisolone) only sparingly, if at all — why, see below.

02

Sugar only with symptoms

Don't give glucose preventively. Preventive sugar drives the tumour to produce even more insulin — afterwards the value drops lower. Only small amounts during acute hypoglycemia with symptoms, then check.

03

Read the dog, not just the values

Voice, alertness, personality. A changed bark, fading attention — these often reveal the course earlier than any lab result.

04

Get several opinions

Insulinoma is not trivial. Your regular vet, a specialist practice and a clinic with CT — this triple safeguard helped us not to miss anything.

05

Stay realistic

Insulinoma is not curable. Everything you do buys time — no one buys a cure. Accepting that from the start lets you walk the road without inflated expectations.

06

The dog communicates its end

Refusing food and tablets is the clearest language. Those who listen know when it is time. That is not giving up — that is respect.

Honest about the intensity of care: 24/7 monitoring, daily dose adjustments, immediate response to alarms over months — that is only manageable as a team and under certain life circumstances. This depth was carried by two people: Patric could monitor and dose during the day because he is self-employed and works from home; Nicole took over the morning care and feeding before work and lovingly handled the meals in the evening. Anyone who has to manage this alone alongside a full-time job can hardly provide that depth — that is not a problem of love, but a structural one. Discuss realistic options for your situation with your vet.

The course, in brief

  1. January 2024

    Mammary carcinoma surgery (grade II), removed cleanly. The first serious diagnosis.

  2. August 2025

    First emergencies, low glucose, neurological symptoms. Insulinoma suspected — confirmed biochemically (insulin 158 pmol/l during hypoglycemia).

  3. September 2025

    Second opinion at a specialist practice, start of parallel co-care over 8 months.

  4. April 2026

    Second major crisis, CT diagnostics: a multi-system process, no sensible surgical option. Switch to deliberate palliative care.

  5. April–May 2026

    Seven mostly good weeks. Often completely herself again.

  6. Whitsun 2026

    Sudden collapse of the control. No medication worked anymore. A supported, dignified farewell.

The cost reality

Honest figures — so no one starts out with false ideas:

around €8,000
The insulinoma phase over 9 months — including the veterinary clinic & diagnostics with CT (~€4,260 documented), specialist Dr. Paulus (~€2,000), plus CGM sensors, special food and medication.

On top of that comes what cannot be quantified: time, sleepless nights, constant presence.

The big decision

Surgery — yes or no?

Surgery can be the best chance for a lot of good time — or an unnecessary burden. It depends on the timing. There is no blanket answer; everyone has to decide it for themselves.

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An extreme procedure

Pancreatic surgery is major and demanding. Recovery takes time — depending on age, a good two months, if the dog comes through it well at all. That has to be factored in honestly.

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Caught early & operable: worthwhile

If the tumour is detected early, clearly defined and without metastases, surgery in my opinion offers the most — the studies also show the longest survival times here. Then it is worth seriously considering.

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Late / with metastases: rather no

At an advanced stage, with metastases or several affected organs, in my view the burden outweighs the benefit — not recommended. That was also the case with Pebbels.

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Clarify at once — don't wait!

If the diagnosis comes early, immediately determine whether surgery is possible: CT or MRI with contrast, and ultrasound with Doppler if needed. Don't wait — with insulinoma, clarity gained early matters.

Note: A personal assessment from Pebbels' course, not veterinary advice. Always clarify operability, anaesthetic risk (especially in brachycephalic breeds such as the French Bulldog) and prognosis with your vet and surgeon.

Medication tip

Understanding diazoxide (Proglycem)

The main medication for insulinoma — and what really matters. From our own experience, not from a textbook.

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It raises blood sugar

Diazoxide slows the tumour's insulin release and boosts the liver's glucose output — the counter to the insulin excess.

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It can overshoot

Dose-dependent: a strong dose (e.g. 100 mg) can drive the glucose up sharply — with Pebbels, at times up to ~300 mg/dl when the tumour happened to be supplying less insulin. "Dose-dependent hyperglycemia" is a known effect.

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Tell day and night apart

During the day, movement burns glucose and keeps it down; at night, at rest, that counterforce is missing — so it tends to overshoot. A sawtooth: drops during the day, highs at night.

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Dose to need

Not stubbornly the maximum dose. Adjust to real values, time of day and activity — in calm, stable phases a smaller dose (e.g. 25 mg) can be exactly right to avoid the overshoot.

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Keep an eye on circulation

Recalculate the prescribed dose (mg/kg). According to the product information (PROGLICEM, section 5.3), in dog studies at high doses 1 in 4 animals died of circulatory failure (hypotension) — watch blood pressure and circulation.

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When it no longer works

If the glucose no longer stays up despite a dose increase, the disease has overrun the medication — "more dose" is then rarely the solution. Cortisone "just to be safe" then often brings more side effects than benefit.

Source & note: Product information PROGLICEM® 25/100 (diazoxide, MSD), section 5.3 "Preclinical safety data". This does not replace veterinary advice — please discuss any dose change with your vet.

A critical view

Cortisone (prednisolone) — only with caution

A clear, personal stance from Pebbels' course: cortisone — much like antibiotics — is often prescribed too readily for all sorts of things. With insulinoma, in our experience, it was more of a burden than a help.

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The one advantage

Cortisone raises blood glucose: it prompts the liver to release its glucose reserves and dampens the action of insulin. That is the desired effect against the hypoglycemia — and basically the only real plus.

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Risk of thrombosis

Cortisone promotes blood clotting and thus the risk of thrombosis. That is exactly what happened with Pebbels — the CT finding showed a thrombosis on the pancreatic vein. With this disease, a particularly serious drawback.

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It attacks the stomach

It irritates the gastrointestinal tract — tricky with an already sensitive stomach. Nausea, heavy drooling and gastritis were part of her hard hours.

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Not simply stopped

Cortisone must never be ended abruptly — it has to be tapered off slowly. You tie yourself to a drug you can't simply get rid of again.

Our recommendation: Consider cortisone for insulinoma only as a last resort. In hindsight, we would start with diazoxide (Proglycem) alone — or an injection therapy. That would have spared Pebbels some hardship and perhaps even given her more time.

What the research says — to be fair: In the specialist literature, prednisolone is regarded as a recognised second-line agent for insulinoma. A study linked below (Polton 2007) even showed longer survival times in dogs that received prednisolone at relapse. Our stance above is therefore deliberately more cautious than the research consensus — but the side effects mentioned are real and documented. Weigh both up and decide with your vet.

Note: This is Patric's personal assessment from the course of the illness — not veterinary advice. Cortisone also has legitimate uses (for example with inflammation/pancreatitis), and every case is different. Please always discuss the choice and any withdrawal with your vet — abrupt discontinuation can be dangerous.

From practice

Three lessons that save lives

Knowledge that counts in an emergency — often only learned there. Known in advance, it can make all the difference for the next little mouse.

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Exercise lowers blood sugar

In a healthy dog, activity raises blood glucose. With insulinoma it flips: every rise triggers an insulin avalanche from the tumour — the glucose crashes instead of rising. So take walks only in stable phases, keep them short, with CGM; measure before and after, always carry emergency glucose.

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"Slept soundly" doesn't mean "all is well"

In sleep everything seems stable — little consumption, yet the tumour keeps releasing insulin. The dangerous lows often come on waking: a sudden demand, an insulin avalanche, a crash within minutes. Long rest periods without CGM monitoring are especially risky.

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How to recognise a real emergency

Three signs together = confirmed severe hypoglycemia: a low glucose value + matching symptoms (see warning signs below) + rapid improvement after glucose (Whipple's triad). When in doubt, cross-check the CGM value with the blood glucose meter — then act immediately.

The warning signs — from quiet to life-threatening

Early & quiet (often missed): restlessness, increased panting, scratching at the blanket or floor, looking disoriented/unsettled when lying down, unable to find any peace.

Clear (hypoglycemia underway): weakness, staggering (ataxia), trembling, changed behaviour, an empty stare.

Severe (very low glucose — act at once): loss of function, brief blackouts up to unconsciousness, seizure. Now every minute counts.

Note: Experience-based knowledge from Pebbels' course — not veterinary advice. Please always discuss emergency measures and dosages with your vet.

Further reading

Studies & Sources

Evidence and in-depth literature on insulinoma in dogs — from the diazoxide study to the major outcome studies. For anyone who wants to dig deeper or speak to their vet well-informed.

The medication: diazoxide (Proglycem)

Course, treatment & prognosis

Note: Mostly English-language specialist literature — it does not replace veterinary advice, but it helps you go into the conversation with your vet well-informed.

What helps in the bowl

Nutrition with insulinoma

Here too a double-edged sword: the body needs a lot of energy — and at the same time a long, slow digestion that keeps the glucose stable. Diet food and high-energy food pull in opposite directions, and so do the studies. Our advice: the middle path.

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No diabetic food

The most common mistake: diabetic food is made for blood sugar that is too high — but with insulinoma it is too low. We figured this out ourselves, against the first recommendation.

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The middle path — by time of day

Protein + complex carbohydrates (rice, oats, potato) for slow energy, mixed with a bit of high-energy food. And dose it by time of day: more slow diet food at night — it releases glucose evenly across the long night and cushions the morning lows; more energy in the morning, because during the day movement pulls the glucose down. Many small meals, no fast sugars.

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No time to cook?

It works without cooking fresh too: just mix the two ready-made foods — diet food and high-energy or normal food, in roughly equal parts. That way you hit the middle path even on hectic days.

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Purée & by syringe

When she wouldn't eat on her own: purée the food with a blender and give it by syringe. For us this worked wonderfully — at first a welcome service, in the final days a gentle nudge. In between she would eat all on her own again.

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Don't skimp on treats

We didn't skimp on her favourite snacks. When time is limited, the dog should have every advantage it can get — joy is part of the therapy.

The food was above all Nicole's domain: in the morning before work, in the evening with calm and patience — and she tirelessly sought out treats and favourite foods. Without her this part would not have been possible.

"Chance of a cure: zero — but quality of life at 200%. Only that makes sense to me."— Patric

Note: Experience-based values from Pebbels' course, not veterinary advice. For acute hypoglycemia with symptoms, give small amounts of fast sugar (e.g. honey) — but never preventively, that only drives the tumour all the more. Please discuss the feeding plan and emergency procedure with your vet.

A closing word

When it is time

Don't make the mistake of letting your animal suffer needlessly out of love. A dog fights to the very end — that is its nature. It will never ask you for release.

That is exactly why it is the owner's hardest and at the same time most loving task: to make the decision about when it is time to go. The dog does not carry this burden — you carry it for him.

And anyone who truly knows their dog feels that point: in the spark gone out, in the refusal of food, in the gaze that is no longer the same. Letting go is then not giving up. It is the last service of love.