Last updated: April 9, 2026
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Can Dogs Eat Tuna Water? Only as a Rare Treat
Dogs can drink small amounts of tuna water occasionally, but it should not become a regular part of their diet. The liquid from a can of tuna, often called tuna water or tuna juice, is not toxic to dogs in small quantities, but it carries two significant concerns: mercury and sodium. Both can cause health problems with repeated exposure.
If you are going to share tuna water with your dog, choose water-packed tuna (not oil-packed), select low-sodium varieties, and limit it to a tablespoon or two as a very occasional treat. This is one of those foods where the answer is “technically safe but not recommended as a habit.”
For safer ways to give your dog the benefits of fish, our guide on salmon skin for dogs covers a lower-mercury alternative.
Mercury in Tuna: Why It Matters for Dogs
The primary concern with tuna products for dogs is mercury. Tuna is a large, predatory fish that accumulates methylmercury through a process called bioaccumulation. As tuna eat smaller fish that contain trace amounts of mercury, those trace amounts concentrate in the tuna’s tissues over its lifetime.
Mercury levels vary significantly by tuna species:
- Albacore (white) tuna: Contains approximately 0.35 parts per million (ppm) of mercury on average. Some cans test higher.
- Skipjack (light) tuna: Contains approximately 0.12 ppm of mercury. This is the better choice if you are going to offer tuna water to your dog.
- Yellowfin and bigeye tuna: Higher mercury levels, often used in sushi-grade products rather than canned tuna.
While the tuna water itself contains less mercury than the flesh, mercury is water-soluble and does leach into the liquid. A small amount once in a while is unlikely to cause harm, but regular consumption adds up. Mercury accumulates in the body and is cleared slowly, meaning frequent small exposures can eventually reach harmful levels.
Signs of Mercury Toxicity in Dogs
Mercury poisoning from occasional tuna water is extremely unlikely, but dog owners should know the warning signs in case of excessive consumption over time:
- Tremors or difficulty walking
- Loss of coordination
- Vision changes
- Hair loss
- Kidney damage (increased thirst and urination, decreased appetite)
- Anxiety or nervousness
- Vomiting and diarrhea
If you suspect mercury toxicity, contact your veterinarian immediately. Treatment may include chelation therapy and supportive care.
Sodium Content: The Hidden Problem
The second major concern with tuna water is sodium. Even tuna canned in water contains significant amounts of salt, which is added during processing to preserve the fish and enhance flavor.
A typical can of tuna packed in water contains 200 to 400 milligrams of sodium. Some brands run even higher. The tuna water absorbs a substantial portion of this sodium. For context, a healthy 30-pound dog needs only about 100 milligrams of sodium per day from all dietary sources combined.
A few tablespoons of regular tuna water could provide your dog with their entire daily sodium allowance or more. This is particularly problematic for dogs with:
- Heart disease: Excess sodium increases blood pressure and can worsen congestive heart failure.
- Kidney disease: Impaired kidneys struggle to process excess sodium, leading to fluid retention and elevated blood pressure.
- Liver disease: Sodium can exacerbate fluid accumulation in the abdomen (ascites) in dogs with liver conditions.
Low-sodium or “no salt added” varieties of canned tuna are available and are a significantly better choice if you want to share tuna water with your dog. These typically contain 40 to 80 milligrams of sodium per can, a much more manageable amount.
Safe Portion Sizes and Frequency
If you decide to give your dog tuna water as an occasional treat, following strict portion guidelines minimizes the mercury and sodium risks.
How Much Tuna Water Is Safe
- Small dogs (under 20 lbs): 1 tablespoon, no more than once per week
- Medium dogs (20 to 50 lbs): 1 to 2 tablespoons, no more than once per week
- Large dogs (50 to 90 lbs): 2 to 3 tablespoons, no more than once per week
- Giant breeds (over 90 lbs): Up to 1/4 cup, no more than once per week
Best Practices
- Choose light (skipjack) tuna packed in water over albacore.
- Select low-sodium or no-salt-added varieties whenever possible.
- Pour the tuna water over your dog’s regular food as a flavor enhancer rather than serving it as a standalone drink.
- Do not give tuna water on the same day you feed any other fish products to avoid stacking mercury exposure.
- Keep a mental note of how often you are offering tuna products. Once per week is the maximum recommended frequency.
Many dog owners find tuna water useful for encouraging a picky eater to finish their regular food. The strong fish smell is highly appealing to most dogs. If you use it for this purpose, keep it as infrequent as possible and look for lower-risk alternatives for everyday use, such as low-sodium chicken broth.
Tuna Water vs Other Fish-Based Treats
If your dog loves the taste of fish, there are several alternatives to tuna water that provide similar benefits with fewer risks.
Salmon broth or cooking liquid: Salmon is lower in mercury than tuna and rich in omega-3 fatty acids. If you cook salmon for yourself, the unseasoned cooking liquid can be a safer alternative to tuna water for your dog. Always ensure the salmon was cooked thoroughly without onion, garlic, or heavy seasonings.
Sardine water: Canned sardines in water (no salt added) produce a liquid that is lower in mercury than tuna water because sardines are small fish with short lifespans. The sardine liquid also contains omega-3s and is generally well-tolerated by dogs.
Fish oil supplements: If your goal is to provide omega-3 fatty acids for skin, coat, and joint health, a quality fish oil supplement formulated for dogs eliminates the mercury and sodium concerns entirely. These supplements use purified fish oil with mercury removed.
Dried fish treats: Dehydrated fish treats made from low-mercury species like whitefish or salmon provide the fish flavor dogs love in a convenient, shelf-stable format. Look for single-ingredient treats with no added salt or preservatives.
Each of these alternatives offers the fishy flavor that makes tuna water so appealing to dogs while presenting a better safety profile for regular use.
What to Do If Your Dog Drank a Lot of Tuna Water
If your dog got into a can of tuna water or drank more than the recommended amount, here is how to respond based on the situation.
Single incident, small to moderate amount: If your dog drank the liquid from one can of tuna, the most likely outcome is no symptoms at all, or possibly mild digestive upset. Provide plenty of fresh water to help flush the excess sodium, and monitor for vomiting, diarrhea, or increased thirst over the next 12 to 24 hours.
Single incident, large amount (multiple cans): This is more concerning due to the sodium load. Signs of excessive sodium intake include extreme thirst, vomiting, diarrhea, lethargy, and in severe cases, tremors or seizures. Provide unlimited fresh water and contact your veterinarian, especially if your dog is small or has pre-existing heart or kidney conditions.
Chronic overconsumption: If you have been giving your dog tuna water daily for weeks or months, the mercury accumulation is the primary concern. Discontinue all tuna products and mention the tuna water habit at your next veterinary visit. Your vet may want to run blood work to check kidney function and general health markers.
For more information on keeping your dog safe and healthy, visit our dog care resources. If you are thinking about adding a furry friend to your family, check out the adoptable dogs on our dog adoption page.
Frequently Asked Questions
Is tuna water from fresh tuna safer than from canned tuna?
The liquid from cooking fresh tuna at home does not contain the added sodium found in canned tuna, making it safer from a sodium standpoint. However, the mercury concern remains the same since mercury is present in the fish flesh itself. If you cook fresh tuna without seasoning, the cooking liquid is a slightly better option than canned tuna water, but still should be limited due to mercury.
Can tuna water help a sick dog eat?
The strong aroma of tuna water can sometimes entice a dog with a reduced appetite to eat their regular food or a bland recovery diet. A small amount drizzled over food may help during short-term illness. However, if your dog is sick enough to refuse food, the underlying cause needs veterinary attention. Do not rely on tuna water as a long-term appetite stimulant when safer options like low-sodium chicken broth exist.
Can cats have tuna water if dogs should limit it?
Cats face similar mercury and sodium concerns with tuna water. While cats are often more attracted to tuna than dogs are, the same guidelines apply: small amounts of low-sodium tuna water as a rare treat only. Cats are also susceptible to developing a “tuna addiction” where they refuse all other foods, which leads to nutritional deficiencies. Keep tuna water as an occasional treat for both species.
Does rinsing canned tuna reduce the sodium in the water?
Rinsing canned tuna under water can reduce the sodium content of the flesh by 40 to 80 percent, depending on how thoroughly you rinse. However, the tuna water itself, the liquid you would give your dog, has already absorbed the sodium during the canning process. If you want to reduce your dog’s sodium intake from tuna, drain and rinse the tuna before offering a small piece of the flesh instead of the liquid.
How do I know if my dog is getting too much mercury from fish products?
Mercury accumulation happens gradually and early stages may not show obvious symptoms. If you regularly feed your dog tuna, swordfish, or other high-mercury fish, mention this to your veterinarian. They can monitor kidney function and overall health through regular blood work. As a practical guideline, limit all high-mercury fish products to once per week at most, and choose lower-mercury options like salmon, sardines, and whitefish for more frequent fish treats.
