DENVER (CBS4) – Dog owners could pay dearly if their pup gets hold of a penny. There’s an element in the coin that could be deadly to dogs.

If the penny was minted after 1982, it could be a lethal problem. A veterinarian told CBS4’s Kathy Walsh they see a case every three or four months.

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“Everybody loved Sierra and Sierra loved everybody,” dog owner Maryann Goldstein said.

The West Highland white terrier was Goldstein’s tiny shadow and a furry member of the family.

“I used to call her my walking heart on four legs; just one of the nicest dogs,” Goldstein said.

To Goldstein, Sierra was priceless. Sadly, it was a penny that took her life.

“She for some reason had some type of attraction to change,” Goldstein said.

When Sierra was a puppy, she swallowed 32 cents. The money was removed and the problem was solved. But in March, Sierra got very sick. An X-ray showed a quarter and a penny in her stomach.

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“I couldn’t believe it … that she ate change again. I just couldn’t believe it, and this time she wasn’t so lucky.”

The penny was poison. Pennies minted after 1982 are copper with a zinc core.

“The stomach acid eventually digests the penny and releases the zinc into the system,” veterinarian Dr. Jenna Ashton said.

Ashton says that causes red blood cell destruction, leading to kidney and liver damage.

“They die from lack of oxygen,” Ashton said.

By the time experts at the Veterinary Referral Center of Colorado found the penny, Sierra was dying.

“There’s nothing I can do, she’s just simply gone,” Goldstein said.

Goldstein wears some of her little dog’s ashes in a necklace. The rest are in a heart-shaped container. She knows Sierra’s case was extreme, but tells the story to warn others that a one cent coin could cost people a loving companion.

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Ashton says some of the signs of zinc poisoning in dogs are pale gums, lethargy and vomiting. Get a dog to the vet immediately if the dog shows those symptoms.