It is common to see worms in your dog's stools following treatment for deworming. However, deworming a dog may have other effects, including digestive upsets, lethargy and eventual positive health changes.
Dog-worming products are used to free the dog of parasites. It is normal to see whole worms or pieces of worms in the dog's stools for a short period after worming. According to VetInfo.com, some medications only paralyse the worms before they are expelled, resulting in live worms appearing in the dog's stool.
According to The-Puppy-Dog-Place website, dogs may experience an upset stomach or diarrhoea after deworming. Your dog may vomit a bit after deworming, maybe even bringing up some worms. While unpleasant, this effect is normal and simply indicates that the medication working. As with vomiting, diarrhoea is a normal effect of deworming. Repeated bouts of vomiting or diarrhoea, however, or expulsion/excretion of a lot of worms is cause for concern and the dog's vet should be consulted.
Lethargy and other temporary effects
After deworming, some dogs or puppies may lack energy or appetite, just as they might if they have a mild reaction to a vaccination. While mild symptoms are nothing to worry about, call the vet if this behaviour lasts more than a day or two or if your dog seems to be in distress.
Positive physical effects
Dogs should feel better about 24 hours after worming. If your dog has lost coat condition or has experienced other physical effects, it should gradually return to good health. A new faecal exam should be undertaken two weeks after the first treatment to ensure all the worms have been eliminated.