Puppies which are 6-8 weeks old. 8 weeks old
You should start your puppy on a heartworm preventative medication as soon as he's 8 weeks old. Lots of vets give a free sample of Heartgard for pups at their first puppy check up, after that it's up to you. These medicines need to be given once a month (without fail), during mosquito season.  It’s getting warmer outside — time for sellers of heartworm medications to start scaring you to death. Television and print ads, which used to push meds only during warm summer months, now urge you to keep your dog on medication year round.  All dogs should start on regular heartworm prevention medicine when they are puppies. Most heartworm prevention medicines are safe for puppies as young as 6-8 weeks old. If you give your dog his heartworm “prevention” on April 1, and he gets bitten by a mosquito on April 2, he can get infected with baby heartworms. If you give the next dose of prevention on May 1, that medicine will kill the 8 weeks is the youngest you can start giving heartworm prevention, and starting as soon as you can is recommended. When you take your pup in for his checkup (usually in the first week you have him) your vet can get you started. Source(s): Vet Tech. Emdee · 5 years ago.  If the animal is off Heartgard Plus for 6 months or less, start the medication and test after 6 months since microfilaria, that take 6 months to mature, will result in a positive test result. Store Heartgard Plus at room temperature. Do not remove the tablet from its wrapper until ready to give the medicine.  My pup had his first heartworm tablets at 13 weeks old. However, you shouldnt give a dog over the age of 6 months any heart worm tablets etc if he hasnt first been heart worm checked as it is possible for dogs to die if they are given heart worm medication and they already have heartworm. lys · 8 years ago. Thumbs up. 2. Thumbs down. Even better, we will send you postcard and email reminders when it is time for your dog to get his next dose! Proheart 6 can only be used in dogs older than 6 months. Puppies should start on a monthly heartworm prevention by the time they are 8 weeks old, and can start using Proheart 6 when they are six months old. If you give your dog his heartworm “prevention” on April 1, and he gets bitten by a mosquito on April 2, he can get infected with baby heartworms. If you give the next dose of prevention on May 1, that medicine will kill the [Back to top] When should I start my puppy or kitten on a heartworm prevention program? Some heartworm preventives can be given to puppies as young as 4 weeks of age, and kittens at 6 weeks of age. Consult with your veterinarian and consider the preventive you choose.  Prevention. Typically, you should begin heartworm treatment in puppies around 6 to 8 weeks of age, although some heartworm preventatives are suitable for even younger dogs. Once a dog reaches 6 months of age, however, you should not begin a preventative cycle without first having your dog tested for infection. 
http://www.fidosavvy.com/heartworm-prevention.html http://www.dogs4dogs.com/blog/2009/05/13/heartworm-medication-safety/ http://princetonvet.net/when-should-i-start-my-dog-on-heartworm-prevention/ https://answers.yahoo.com/question/index?qid=20100925112920AAWgJ4c http://www.1800petmeds.com/Heartgard+Plus+Chewables-prod10002.html https://answers.yahoo.com/question/index?qid=20080326164224AAjscaD http://princetonvet.net/when-should-i-start-my-dog-on-heartworm-prevention/ http://www.drsfostersmith.com/pic/article.cfm?aid=582 http://dogcare.dailypuppy.com/start-heartworm-meds-dogs-5604.html
when should i start heartworm medication