The dog’s mouth smells like metal.

Dental Disease

Many dog breeds are prone to dental issues, especially breeds with short snouts and crowded teeth, such as French Bulldogs and Pugs, as well as dogs with small mouths like Yorkies. Regardless of breed, a dog can develop dental disease at some point in its life.
Dogs don’t brush their teeth two or three times a day like humans do, and they generally eat poorer quality food, making them highly susceptible to dental problems.
Dental disease can develop at any age, but it is more common in older dogs. When a dog has dental disease, gum irritation is likely present. Bleeding gums are often observed, though it can be subtle. This can result in a metallic smell from the mouth, but the overall consequences of dental disease can lead to such a smell.

Anal Glands

Dogs have two small glands located inside the rectum. These glands are modified scent glands, often referred to as “smelly.” A dog’s anal glands empty when they defecate, but some dogs may struggle to empty them naturally. This can be caused by various factors, including body weight, diet, anatomy, tumors, illnesses, and genetics.
Dogs with full anal glands are likely to begin licking their rear in an attempt to relieve the irritation. This often leads to small amounts of anal gland secretion getting into the mouth, which can result in a metallic smell. The odor from the anal glands is typically associated with a distinct fishy smell, but it often has a metallic undertone.

Kidney Disease

Kidney disease is a very serious condition that will ultimately lead to kidney failure in dogs. Even with treatment, kidney disease will progress, eventually leading to complete renal failure. A metallic smell from a dog’s mouth could be a sign of kidney disease.
This odor is caused by the accumulation of waste products in the body due to the kidneys’ inability to filter out these toxins. In healthy kidneys, waste products are excreted through urine, but when the kidneys are diseased, they fail to do so. The metallic smell associated with kidney disease is also somewhat reminiscent of ammonia.

Diabetes

When a dog has diabetes, its body is unable to produce enough insulin to keep blood sugar levels in check. That’s why diabetic dogs are given insulin as part of their daily treatment plan. In dogs that do not receive enough insulin or have not been diagnosed with diabetes, the body loses the ability to break down glucose into usable energy.
To obtain the necessary glucose, the body starts breaking down its own fat stores, leading to ketosis, which ultimately results in diabetic ketoacidosis, a life-threatening condition. When the body enters ketosis or ketoacidosis, the dog’s breath takes on an unusual odor. This is often described as “sickly-sweet,” but it may also have a metallic taste.

Oral Tumors

Oral tumors in dogs can be hard to detect. Most people are not very familiar with the inside of a dog’s mouth, and tumors can appear anywhere, even in hard-to-reach places. Oral tumors can be hidden and may grow significantly before they are noticed.
A strong, unpleasant odor from the mouth is often the first sign of an oral tumor. Sometimes, it can have a metallic undertone due to the body’s reaction to the tumor. Oral tumors can be difficult to treat if not noticed in time, so any new growths or lumps in a dog’s mouth should be examined by a vet.

Coprophagia and Pica

Coprophagia is the consumption of feces, and some dogs simply love to eat it, which inevitably leads to foul-smelling breath. Pica refers to the consumption of non-food items, such as paper, wood, shoes, etc.
Most of the time, the unpleasant smell from a dog’s mouth will simply remind you of whatever the dog has eaten. However, depending on the dog’s diet, health, and other factors, the smell of their feces can vary greatly.

Blood

The smell of blood can be described as metallic. There are many reasons a dog might have blood in its mouth, leading to this corresponding odor. If a dog has a bleeding oral tumor or gum disease, a metallic smell may come from its mouth.
Regardless of whether the blood is coming from the mouth or another source, it can leave behind a strong metallic odor.

Internal Bleeding

It’s important to distinguish between blood in the dog’s mouth and internal bleeding. If a dog suddenly develops a metallic smell from its mouth and the cause is unclear, a visit to the vet is necessary.
Internal bleeding can lead to a metallic smell from the mouth, but it may be difficult to identify an external factor, such as a tumor or gum irritation.
Internal bleeding is usually accompanied by other symptoms, such as pale gums, black or bloody stool, bloody vomiting, and abdominal bloating. If there is any suspicion that a dog might be suffering from internal bleeding, it must be taken to the vet immediately.