Why Is My Dog With Cancer Panting?

Panting in a dog with cancer almost always comes down to one of four things: pain, a medication (most often a steroid or an opioid), a problem getting oxygen into the bloodstream, or anxiety and restlessness. Pain is the most common cause, and it's also the one owners are most likely to miss, because a lot of dogs in real discomfort never whimper or limp. They just breathe harder than they should.

The single most useful thing you can do is watch when the panting happens. A dog who pants after a walk on a July afternoon is doing what dogs do. A dog who pants lying on a cool floor at two in the morning, in a quiet house, with nothing going on, is telling you something. That second pattern deserves a call to your veterinarian, not a wait-and-see.

Key points

• Panting at rest, in a cool room, is the pattern that matters. Context is what separates normal from abnormal.
• Pain is the leading cause, and dogs hide it well. As end-of-life care veterinarian Dr. Dawnetta Woodruff writes, "Panting can also mean that dogs aren't getting enough oxygen."
• Prednisone is a very common culprit. Panting shows up in a large share of dogs on steroids, and it often starts within the first week.
• Panting and labored breathing are not the same thing. Labored breathing is an emergency. Learn to tell them apart.
• Pale, white, blue, or grey gums alongside panting means go now, not in the morning.
• Counting your dog's breaths while they sleep gives your vet a number to work with instead of a guess.
• If your dog is on tramadol for pain and still panting, the medication may not be doing much. That's worth raising.

Detailed explanation

Start with what normal panting does

Dogs don't sweat the way we do. Panting is their radiator. Fast, shallow breaths move air across the wet surfaces of the tongue, mouth, and upper airway, and evaporation carries heat away. Normal panting has a rhythm to it. It starts when a dog is hot, excited, or has just been running, and it winds down within several minutes once the dog rests somewhere cool.

Cancer changes the picture because it adds a long list of reasons a dog might breathe fast that have nothing to do with temperature. Sorting through them is the job.

Pain is the most common reason

This is where to start, because it's the most likely answer and the most treatable one.

Dogs evolved to hide pain. A dog with a bone tumor may still eat dinner, still wag, still meet you at the door, and still be in real distress. The outward signs are often small: restlessness at night, trouble settling into a comfortable position, licking at one spot, reluctance to jump onto the couch, and panting. The 2022 AAHA Pain Management Guidelines make the point that owners are the ones who know what normal looks like for their own dog, and that changes from that baseline are meaningful evidence of pain (Gruen et al., 2022).

The cancers most often behind pain-driven panting are the ones that press on or invade something. Bone tumors like osteosarcoma are notoriously painful. So are large abdominal masses, tumors in the mouth or nose, bladder tumors that make a dog feel like they constantly need to urinate, and any tumor that has ulcerated or become infected.

Veterinary hospice teams see this pattern constantly. Lap of Love's clinicians note that "Signs of pain include limping, trembling, vocalizing, panting, or flinching," and that some dogs withdraw and hide rather than show anything at all.

There's a common misconception worth clearing up here. Many owners assume that a dog already on pain medication must therefore be comfortable. Not necessarily. Tramadol in particular is widely prescribed and poorly supported by evidence in dogs. Dogs don't reliably produce enough of the active metabolite that provides the pain relief, and a randomized, blinded, placebo-controlled trial found tramadol performed no better than placebo in dogs with osteoarthritis (Budsberg et al., 2018). Dr. Steven Budsberg, who led that study, put it plainly: "tramadol is not an effective drug in treating the pain associated with arthritis." If your dog is panting through a tramadol prescription, that's a conversation to have, not a sign that nothing more can be done.

Steroids and other medications

If your dog started panting shortly after a new prescription, look at the prescription.

Prednisone and prednisolone are used constantly in canine cancer care, and increased panting is one of their most common side effects. In a study of owners giving anti-inflammatory doses of prednisone or prednisolone, 74% reported at least one behavior change by day five, and 90% reported at least one by day 14, with rapid breathing among the most frequently mentioned changes (Gober & Hillier, 2023). At higher immunosuppressive doses, the numbers climb further. One report summarized in the Canadian Veterinary Journal found excessive panting in 81% of dogs on a high daily dose (Sri-Jayantha et al., 2022).

Steroid panting is usually worst in the first week or two, often peaks at night, and tends to ease as the dose comes down. It's uncomfortable to watch and it wrecks everyone's sleep, but on its own it isn't dangerous. Tell your vet about it anyway, because the dose or the schedule may be adjustable.

Opioids do something different. In dogs, drugs like morphine and hydromorphone act on the temperature-regulating center in the brain, and panting is the visible result. It's such a consistent effect that studies measuring opioid side effects in dogs track it as a standard outcome (Claude et al., 2014). Dogs on opioids for cancer pain frequently pant, and it doesn't mean the drug isn't working. It usually means the drug is on board.

When panting means the body can't get enough oxygen

This is the category that turns urgent fast.

Panting and labored breathing look superficially similar and mean very different things. A panting dog is moving air easily. A dog in respiratory distress is working at it. Watch for an extended neck and head held low and forward, elbows pushed away from the chest, the belly heaving with each breath, or a dog who won't lie down on their side because it's harder to breathe that way. Any of that is an emergency.

Several cancer-related problems reduce oxygen delivery:

Tumors in the lungs. Cancer that has spread to the lungs, or a primary lung tumor, can take up enough functioning tissue to make breathing inefficient. Worth knowing: lung tumors are often quiet for a long time. Up to about 30% of dogs with primary lung tumors have no signs at all when the tumor is found, which is part of why staging chest imaging matters even in dogs who seem fine.

Fluid around the lungs or heart. Fluid in the chest cavity compresses the lungs. Fluid in the sac around the heart, called pericardial effusion, keeps the heart from filling properly. Heart-based tumors and hemangiosarcoma of the right atrium are common causes in dogs. The team at NC State's veterinary hospital lists among the signs "labored breathing, increased resting breathing rate, exercise intolerance," alongside weakness, collapse, pale gums, and a distended belly. Pericardial effusion can go from mild to life-threatening in hours.

Anemia. Fewer red blood cells means less oxygen carried in each breath, so the body compensates by breathing faster. Anemia in a dog with cancer can come on slowly (chronic disease, bone marrow involvement, chemotherapy effects) or catastrophically. A ruptured splenic or hepatic tumor bleeding into the abdomen produces sudden weakness, pale or white gums, a swollen belly, and fast breathing. That is an emergency room situation.

Airway obstruction. Masses in the nose, throat, larynx, or windpipe make air physically harder to move. These dogs often make noise when they breathe. Older large-breed dogs can also develop laryngeal paralysis, which is unrelated to cancer but looks alarming and worsens in heat and excitement.

Gum color is the quickest home check you have. Lift the lip and look. Healthy gums are pink and moist. Pale pink, white, blue, grey, or muddy red are all reasons to leave for the vet immediately.

Metabolic and whole-body causes

Some cancers change body chemistry in ways that make dogs feel awful without any direct effect on the lungs.

High blood calcium, or hypercalcemia of malignancy, is the most common of these. It shows up most often with lymphoma and with anal sac tumors. The classic signs are dramatic thirst, dramatic urination, weakness, lethargy, and nausea (Ham, 2024). Dogs who are nauseated, dehydrated, and weak often pant, so hypercalcemia can be part of the picture even though it isn't a respiratory problem. It's diagnosed with bloodwork, specifically ionized calcium, and it's treatable.

Fever is another. Panting is one way a dog sheds heat, so a dog running a temperature will often pant. In a dog receiving chemotherapy, a fever is not something to monitor at home. Low white blood cell counts after chemotherapy can allow infection to escalate quickly, and fever in that window is treated as an emergency by every oncology service.

Nausea itself causes panting, along with drooling, lip licking, and repeated swallowing. Anti-nausea medication often resolves it within a day.

Anxiety, restlessness, and the two-in-the-morning problem

Not every cause is physical. Dogs with cancer are often taken to unfamiliar buildings, handled by strangers, given medications that make them feel odd, and separated from their routines. Anxiety produces panting, pacing, and an inability to settle.

Older dogs may also have canine cognitive dysfunction layered on top, which classically disrupts the sleep-wake cycle and produces exactly the nighttime pacing and panting that so many owners describe. And pain and anxiety feed each other, which is why it can be genuinely hard to tell them apart from the outside.

The practical approach is usually to treat what you can treat and watch what happens. If a trial of better pain control settles a restless, panting dog within a couple of days, that tells you something useful about what was driving it.

Learn to count breaths

Here is the single most valuable habit for anyone caring for a dog with cancer at home.

Wait until your dog is fully asleep or resting quietly. Watch the chest. One rise plus one fall is one breath. Count for 30 seconds and double it. Do this a few times a week and write the numbers down.

Healthy dogs breathe slowly at rest. In a study of 114 pet dogs measured at home, the average sleeping respiratory rate was around 13 breaths per minute, and no dog averaged more than 23 (Rishniw et al., 2012). Veterinary cardiologists use 30 as the practical alarm line. As the VCA guidance co-authored by cardiologist Dr. Sonya Gordon puts it, resting or sleeping rates "consistently greater than 30 breaths per minute are increased and considered abnormal" (Hunter et al., n.d.).

That number is a gift to your veterinary team. "He's breathing kind of fast" is hard to act on. "He's been sleeping at 44 breaths a minute for two days, up from 20 last week" is a clinical finding.

Panting doesn't count for this measurement. Wait for quiet, closed-mouth breathing.

What this means for quality of life

Panting is one of the items that appears on nearly every quality-of-life framework, including the widely used HHHHHMM scale developed by veterinary oncologist Dr. Alice Villalobos. It's not because panting itself is dangerous. It's because persistent panting at rest, when heat and exercise have been ruled out, is often the outward face of pain or breathing difficulty that a dog is otherwise concealing.

Veterinarian Dr. Lori Gibson frames the decision point this way: when pain medications stop working, "your dog may be suffering more than they're showing."

That's not a reason to panic when your dog pants. It is a reason to take it seriously, get it explained, and treat what's treatable. Most causes of panting have something that can be done about them, and a dog whose pain is finally controlled often sleeps through the night for the first time in weeks.

When to contact a veterinarian

Go to an emergency clinic right now if you see:

• Gums that are pale, white, blue, grey, or muddy red
• Open-mouth breathing that doesn't stop even when your dog is calm and cool
• Visible effort to breathe: extended neck, elbows out, heaving abdomen, refusal to lie down
• Collapse, stumbling, or fainting
• A suddenly swollen or distended abdomen
• Sleeping or resting breathing rate above 40 that stays there
• Fever, especially within two weeks of a chemotherapy treatment

Call your veterinarian the same day for:

• New panting at rest that you can't explain by heat, exercise, or excitement
• Sleeping breathing rate consistently above 30
• Panting with restlessness, pacing, or an inability to get comfortable
• Panting plus a big increase in drinking and urinating
• Panting alongside coughing, exercise intolerance, or new weight loss
• Panting that's clearly getting worse day over day

Bring it up at the next scheduled visit if:

• Panting started within a few days of a new steroid prescription and your dog is otherwise bright, eating, and comfortable
• Panting happens only during or shortly after a dose of pain medication and settles afterward

When you call, have your numbers ready: sleeping breath counts, gum color, when the panting started, what makes it better or worse, and every medication and supplement your dog is currently receiving.

Questions to ask your veterinarian

• Do you think this panting is pain, a medication effect, a breathing problem, or something else? How would we tell?
• Should we do a pain medication trial to see if the panting improves?
• Is my dog's current pain protocol appropriate, or are we relying on a drug with weak evidence behind it?
• Could the panting be a side effect of the steroid dose? Can the dose or timing be adjusted?
• Does my dog need chest imaging to check the lungs, the heart, or for fluid?
• Should we check bloodwork for anemia or a high calcium level?
• What resting breathing rate should I treat as the alarm number for my dog specifically?
• What would you want me to do at 2 a.m. if the panting suddenly gets worse? Where should I go?
• Is it time to involve a veterinary oncologist or a hospice and palliative care veterinarian?
• Are there non-drug things that would help, like changing the sleeping area, cooling, or reducing stress?

Sources

Budsberg, S. C., Torres, B. T., Kleine, S. A., Sandberg, G. S., & Berjeski, A. K. (2018). Lack of effectiveness of tramadol hydrochloride for the treatment of pain and joint dysfunction in dogs with chronic osteoarthritis. Journal of the American Veterinary Medical Association, 252(4), 427–432. https://doi.org/10.2460/javma.252.4.427

Claude, A. K., Dedeaux, A., Chiavaccini, L., & Hinz, S. (2014). Effects of maropitant citrate or acepromazine on the incidence of adverse events associated with hydromorphone premedication in dogs. Journal of Veterinary Internal Medicine, 28(5), 1414–1417. https://doi.org/10.1111/jvim.12414

dvm360. (n.d.). Study shows tramadol has no effect on osteoarthritis pain scores. https://www.dvm360.com/view/study-shows-tramadol-has-no-effect-osteoarthritis-pain-scores

Gibson, L. (2025). When to euthanize a dog with cancer: 8 signs it might be time. https://www.drlorigibson.com/blog/when-to-euthanize-a-dog-with-cancer/

Gober, M., & Hillier, A. (2023). Perception and usage of short-term prednisone and prednisolone in dogs. BMC Veterinary Research, 19, 91. https://doi.org/10.1186/s12917-023-03644-x

Gruen, M. E., Lascelles, B. D. X., Colleran, E., Gottlieb, A., Johnson, J., Lotsikas, P., Marcellin-Little, D., & Wright, B. (2022). 2022 AAHA pain management guidelines for dogs and cats. Journal of the American Animal Hospital Association, 58(2), 55–76. https://doi.org/10.5326/JAAHA-MS-7292

Ham, K. (2024). Hypercalcemia in dogs and cats. Merck Veterinary Manual. https://www.merckvetmanual.com/endocrine-system/the-parathyroid-glands-and-disorders-of-calcium-regulation-in-dogs-and-cats/hypercalcemia-in-dogs-and-cats

Hunter, T., Weir, M., & Gordon, S. G. (n.d.). Home breathing rate evaluation. VCA Animal Hospitals. https://vcahospitals.com/know-your-pet/home-breathing-rate-evaluation

Lap of Love Veterinary Hospice. (n.d.). Signs your dog or cat is dying: End-of-life behaviors to watch for. https://www.lapoflove.com/blog/end-of-life-care-and-euthanasia/signs-dog-or-cat-is-dying-end-of-life-behaviors

North Carolina State University College of Veterinary Medicine. (n.d.). Canine heart-based tumors. NC State Veterinary Hospital. https://hospital.cvm.ncsu.edu/services/small-animals/cancer-oncology/oncology/medical-oncology-canine-heart-based-tumors/

Rishniw, M., Ljungvall, I., Porciello, F., Häggström, J., & Ohad, D. G. (2012). Sleeping respiratory rates in apparently healthy adult dogs. Research in Veterinary Science, 93(2), 965–969. https://doi.org/10.1016/j.rvsc.2011.12.014

Sri-Jayantha, L. S., Doornink, M. T., & Urie, B. K. (2022). Increased risk of select glucocorticoid adverse events in dogs of higher body weight. The Canadian Veterinary Journal, 63(1), 32–38.

Woodruff, D. (2024). Signs a dog is dying of cancer (plus advice for 8 common cancers). Dr. Buzby's ToeGrips for Dogs. https://toegrips.com/signs-dog-is-dying-of-cancer/