It can be worrying when your dog isn’t feeling well after getting vaccinated. Even though vaccines are essential for protection, the hours that follow can come with temporary changes in energy, appetite, and behavior.
This guide outlines the common causes of a dog not feeling well after shots, what you can do at home, and when to seek veterinary help.
Dog Not Feeling Well After Shots: Why It Happens
A dog not feeling well after shots is usually caused by the body’s normal immune response, mild inflammation at the injection site, temporary soreness, or a reaction to the vaccine components. Some dogs may become sleepy, hesitant to move, uninterested in food, or mildly warm to the touch.
These symptoms typically reflect the immune system adapting to the vaccine rather than a sign of illness.
In a few cases, dogs may have stronger reactions that require monitoring or veterinary support. These after-effects often start within a few hours of vaccination and improve within one to two days.
Dog Not Feeling Well After Shots: Common Causes
Normal Immune Response
The most common reason a dog doesn’t feel well after shots is simply their immune system doing what it’s supposed to do. Vaccines stimulate the body to build protection against diseases, and this immune activation can make a dog feel tired or “off.”
When this happens, you may notice your dog sleeping more, eating less, or acting quieter than usual. This reaction is similar to how humans often feel after getting a flu shot: not sick, but not at their best.
This response usually fades within 24–48 hours, and your dog gradually returns to normal as the immune system settles. Although it’s expected, keeping an eye on your dog during this time helps ensure the reaction stays mild.
Related: Dog diarrhea after vaccines (Why it happens)
Injection Site Soreness
Vaccines are commonly given in the shoulder or thigh, and the injection site can become tender or mildly swollen. This localized soreness can make your dog reluctant to walk, jump, or be touched in that area.
Dogs may limp slightly, lick the spot, or flinch when you run your hand over the area. Some dogs even avoid lying on one side because the pressure causes discomfort.
While this soreness is usually mild and temporary, it can make a dog seem unwell because discomfort affects movement, posture, and overall behavior. The area typically improves within a day or two, though some dogs stay sensitive for up to 72 hours.
Mild Fever
Vaccinations can temporarily raise a dog’s body temperature because the immune system is actively responding. A mild fever can cause lethargy, reduced appetite, slower movement, or shivering.
You may notice your dog seeking a cooler place to lie, breathing slightly faster, or feeling warm around the ears, belly, or armpits. This mild fever is not dangerous in most cases; it is a signal that the vaccine is stimulating the immune system appropriately.
However, if the fever persists or rises too high, it may leave your dog noticeably uncomfortable. Monitoring for changes in behavior helps determine if the reaction is within the normal range or something that needs attention.
Vaccine-Related Fatigue or Sensitivity
Some dogs become extremely sleepy after vaccinations. This fatigue is the body’s natural way of conserving energy to support immune function, and it can make your dog reluctant to play, interact, or go for walks.
In some cases, dogs may also become more sensitive to noise, touch, or movement. This can look like clinginess, irritability, or avoiding usual activities.
These symptoms do not necessarily indicate an adverse reaction—they often reflect temporary changes in how the dog feels while their immune system is working. However, if your dog’s fatigue is extreme or lasts more than two days, it’s worth getting a professional opinion.
Gastrointestinal Upset
Although less common, some dogs experience mild digestive upset after shots. Nausea, decreased appetite, drooling, soft stool, or a single episode of vomiting may occur as the body adjusts.
Dogs sensitive to stress or those who are anxious during vet visits may also experience stomach upset unrelated to the vaccine itself. Stress and immune activation together increase the likelihood of mild digestive symptoms.
Digestive reactions should be temporary. If vomiting or diarrhea continues, becomes severe, or contains blood, the cause may be unrelated to the vaccines—or may indicate a rare but important reaction that requires veterinary care.
Mild Allergic Reaction
Some dogs experience mild allergic reactions after vaccinations. This can show up as facial puffiness, itching, hives, redness around the injection site, or sudden tiredness.
Mild allergic reactions typically appear within a few hours of the shot and may cause a dog to feel unwell due to itching, discomfort, or generalized inflammation. These reactions often improve with prompt veterinary treatment.
While mild allergies are manageable, monitoring is crucial because allergic reactions have the potential to escalate in rare cases.
Related: Dog panting and shaking after vaccines (Here’s why)
What to Do If Your Dog Is Not Feeling Well After Shots
Start by letting your dog rest in a quiet, comfortable area of your home. Many dogs benefit simply from sleep, which helps them recover from fatigue or soreness caused by the vaccine. Avoid strenuous activity for the rest of the day to prevent additional stress on their body.
You can offer small amounts of fresh water throughout the day. If your dog seems nauseated or isn’t drinking normally, allow them to sip slowly without forcing intake.
Hydration supports the immune system and helps regulate body temperature if a mild fever is present.
Monitor the injection site gently. If you notice mild swelling or tenderness, you can apply a cool compress wrapped in a soft cloth for a few minutes at a time. This can ease soreness and inflammation. Do not massage the area, as it can worsen irritation.
Feed a normal meal unless your dog refuses food. If appetite is low, try offering something bland and appealing, like boiled chicken or plain rice.
A dog that skips one meal after vaccines isn’t usually a concern, but refusing multiple meals should be taken seriously.
Provide reassurance if your dog seems clingy or anxious. Staying nearby, offering gentle touch, and keeping the environment calm can help reduce discomfort and stress as they recover from the vaccination experience.
When to Call or Visit Your Vet
You should contact your veterinarian if your dog continues to feel unwell for more than 48 hours after shots. Lingering lethargy, ongoing soreness, or persistent appetite changes may indicate a stronger reaction or an unrelated illness triggered around the same time.
Seek immediate veterinary help if your dog shows signs of a severe reaction such as facial swelling, constant vomiting, difficulty breathing, collapse, or sudden weakness. These symptoms can occur within minutes to hours of vaccination and require urgent attention.
If the injection site becomes very swollen, hot, painful, or starts leaking fluid, veterinary evaluation is needed. These signs may indicate infection or a developing reaction at the site that needs treatment.
Contact your vet if your dog has a chronic health condition and shows unusual symptoms after shots. Dogs with weakened immune systems or underlying diseases may have different responses to vaccines and benefit from individualized guidance.
Read more: Dog Suddenly Not Eating and Vomiting (Here’s what may be happening)
Key Takeaway
It’s normal for a dog not to feel well after shots, and most reactions are mild and short-lived.
A bit of tiredness, temporary soreness, or a low appetite usually reflects the immune system doing exactly what it should. Rest, comfort, and close monitoring help most dogs recover smoothly.
But if symptoms worsen, last longer than expected, or appear concerning at any point, your veterinarian is your best resource for keeping your dog safe and healthy.