For many of us, the death of a beloved pet is a death in the family. Deciding to help an ailing dog or cat die fills us with anxiety and pain. How do you know it’s the right time? You don’t want to end a life too soon, but you don’t want to see your four-legged friend suffer needlessly.

“It’s one of the hardest decisions a pet owner has to make, and it’s an emotional one,” says Dan Teich, DVM, who runs the District Veterinary Hospital in Washington D.C. “You have to find the common ground between your feelings and the reality you’re dealing with.”

Related: 6 Coping Strategies to Help You Survive the Death of Your Pet

Is life still enjoyable?

Veterinarians say the most loving, humane response to a pet's decline is to recognize when he or she loses the ability to enjoy life.

Start by looking at the world through the eyes of your pet, advises Andy Roark, DVM, of the Cleveland Animal Park Hospital in Greenville, South Carolina. One way to do it is to think about “The Rule of Five Good Things.” Pick the five things your pet loves to do most. If your pet can no longer do three or more of those things, Roark says, his quality of life is so diminished that many vets would recommend euthanasia.

Teich offers some other questions to consider: Can the pet move freely or at least comfortably? Is his pain out of control? Has he stopped eating, often a sign that the end is near? If he can no longer stand up, walk up and down stairs, or defecate and urinate on his own, he says, his quality of life is poor. If his gums are no longer pink, it’s a sign of reduced oxygen and serious health problem. In this case, euthanasia may be merciful. Similarly, if your pet has a terminal illness and pain that is not eased by medication, he says, it may be time to say goodbye.

You may want to ask your vet whether treatment will improve your pet’s quality of life or merely prolong a poor quality of life. Consider whether you are able to pay for a transplant or medication and extended treatment. And be honest with yourself: Do you want to extend your pet’s life because it’s in the animal’s best interest or yours?

Related: Pet Hospice: Help for Dying Pets

“A lot of people wait for some sort of sign, like a look from the pet,” Teich says. “I get that a lot. They’ll tell me the pet looked at them and basically communicated ‘it’s time.'"

Sometimes the decision is easier, such as after a sudden, catastrophic accident. Declining health as your pet ages is different, Teich says, because it’s not as clear he needs immediate release from suffering.

Getting support

Your vet can help you through end of life decisions, Teich says.

Other sources of support include friends and other pet owners. “You may benefit from having a caring friend who is not as emotionally involved in the situation as you are to help you gain perspective,” says Teich. Pet loss support groups and pet loss hotlines can also provide support “if you just want to talk with somebody,” he says.

“I always tell everybody that we have to come to peace with the fact that pets have a much shorter lifespan than us,” says Teich. “It’s almost like a Shakespearean tragedy because you know what’s going to happen at the end. Unfortunately, friends come and go, and this is one of those sad times when you have to choose the going of your friend.”

If you do decide to put down your pet, The Humane Society of the United States urges you to request injection rather than euthanasia via gas chamber (pet gas chamber deaths involve needless suffering, the society says). As the society puts it, “At the end of a cat or dog's life, the peace of a quiet room, the embrace of someone who cares, and a gentle, painless sleep induced by a trained technician is one of the kindest gifts we can offer a suffering animal.”

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Steve Evans, MA, is an award-winning journalist with more than 20 years experience in daily news, investigative, health and business journalism. Among other jobs, he has served as managing editor of the Central Virginia Newspaper Group, as a senior writer for SNL Financial and as a staff writer for The Progress Index and the Richmond Times-Dispatch.