NexGard for Dogs: Flea & Tick Chewable Protection Guide

Last updated: April 26, 2026

Fleas and ticks are more than a nuisance. They carry diseases, cause relentless itching, and can turn a healthy dog into a miserable one in a matter of days. If you have been researching flea and tick prevention, you have almost certainly come across NexGard — a beef-flavored chewable tablet that has become one of the most popular parasite preventatives on the market since its FDA approval in 2013. This guide covers everything you need to know about NexGard for dogs, including how it works, proper dosing, potential side effects, and the questions worth asking your veterinarian before you start.

What Is NexGard and How Does It Work?

NexGard is a prescription oral flea and tick preventative manufactured by Boehringer Ingelheim. The active ingredient is afoxolaner, which belongs to a class of compounds called isoxazolines. When your dog chews the tablet, afoxolaner is absorbed into the bloodstream and distributed throughout the body. When a flea or tick bites your dog and begins feeding, it ingests the afoxolaner along with the blood meal. The compound overstimulates the parasite’s nervous system, causing uncontrolled activity that leads to paralysis and death.

This mechanism is important to understand because NexGard does not repel parasites — it kills them after they bite. A flea that lands on your dog will still attach and begin feeding, but it will be killed before it can lay eggs. For fleas specifically, NexGard begins killing within four hours and achieves full efficacy within eight hours. For ticks, the process takes a bit longer, typically within 48 hours of attachment. That window matters because tick-borne disease transmission usually requires the tick to remain attached for 24 to 48 hours, so prompt killing reduces the likelihood of infection significantly.

NexGard is effective against several tick species that dog owners commonly encounter, including the American dog tick, the black-legged tick (also called the deer tick, which transmits Lyme disease), the lone star tick, and the brown dog tick. It also kills fleas at every life stage that feeds on the host. If you are adopting a dog and want to start them on a reliable prevention plan from day one, our adoption page includes guidance on transitioning a new dog into your home, including veterinary care basics.

NexGard Dosage by Weight

NexGard is dosed by body weight and comes in four tablet sizes. Each tablet provides 30 days of protection, and the correct dose must be matched to your dog’s current weight. Giving a lower dose than needed can result in incomplete protection, while exceeding the dose is not recommended without veterinary guidance.

• 4.0 to 10.0 lbs: 11.3 mg afoxolaner (orange box)
• 10.1 to 24.0 lbs: 28.3 mg afoxolaner (blue box)
• 24.1 to 60.0 lbs: 68 mg afoxolaner (green box)
• 60.1 to 121.0 lbs: 136 mg afoxolaner (red box)

Dogs weighing more than 121 pounds are typically given a combination of tablets to reach the appropriate dose, which your veterinarian will calculate. NexGard is approved for dogs and puppies eight weeks of age and older, weighing at least four pounds. It is not approved for use in cats, and should never be given to felines.

Consistency matters with any monthly preventative. Give NexGard on the same day each month, and do not skip months — even during winter. Fleas can survive indoors year-round, and ticks are active in many regions whenever temperatures are above freezing. A gap in protection gives parasites an opportunity to establish themselves, and a flea infestation is far more difficult and expensive to treat than it is to prevent.

How to Give NexGard to Your Dog

One of the reasons NexGard has become so popular is its ease of administration. The tablet is a soft, beef-flavored chew that most dogs accept willingly — many treat it as a reward rather than medication. You can offer it with or without food, though giving it with a meal can improve absorption and reduce the small chance of gastrointestinal upset.

If your dog is a picky eater or tends to spit out chewable medications, you can try hiding the tablet inside a small piece of cheese, a dollop of peanut butter (make sure it is xylitol-free), or a soft treat with a pocket for hiding pills. If your dog still refuses, speak with your veterinarian about alternative delivery methods or different preventative options. The full dose needs to be consumed for the medication to work properly, so partial consumption is not acceptable.

After giving NexGard, observe your dog for the first few hours to ensure they do not vomit the tablet back up. If vomiting occurs within two hours of administration, contact your veterinarian to determine whether a replacement dose is needed.

Potential Side Effects of NexGard

NexGard is generally well tolerated by most dogs, and serious adverse reactions are uncommon. However, like any medication, it carries the possibility of side effects, and responsible pet owners should be aware of what to watch for.

The most commonly reported side effects are mild and transient. They include vomiting, diarrhea, dry or flaky skin, lethargy, and decreased appetite. These effects are typically self-limiting and resolve without intervention within a day or two. If symptoms persist beyond 48 hours or worsen, consult your veterinarian.

The more significant safety consideration involves neurological effects. The isoxazoline class of drugs, which includes afoxolaner, has been associated with rare neurological adverse events in dogs, including muscle tremors, ataxia (loss of coordination), and seizures. In 2018, the FDA issued an alert regarding the potential for neurological adverse events with isoxazoline products, including NexGard. The FDA did not pull the products from the market, and veterinary consensus remains that the benefits of parasite prevention outweigh the risks for most dogs, but the alert underscored the importance of discussing your individual dog’s health history with your vet.

Dogs with a history of seizures or neurological disorders require particular caution. If your dog has epilepsy, has experienced seizures for any reason, or has a known neurological condition, your veterinarian may recommend an alternative flea and tick preventative that does not belong to the isoxazoline class. This is not a decision to make on your own — always discuss it with your vet.

Breed Considerations and Safety

NexGard is approved for use across all breeds, and there is no breed-specific contraindication listed on the label. However, some owners of herding breeds — such as Collies, Australian Shepherds, and Shetland Sheepdogs — are understandably cautious about any drug that affects the nervous system, given the well-documented MDR1 gene mutation in these breeds that can affect drug sensitivity.

Current evidence does not indicate that dogs with the MDR1 mutation are at increased risk of adverse effects from afoxolaner specifically, because afoxolaner does not appear to be a substrate for the P-glycoprotein transporter affected by the MDR1 mutation. That said, research on this interaction is ongoing, and the cautious approach is to discuss it with your veterinarian, particularly if your dog has been tested and is known to carry the mutation. You can explore breed-specific health considerations for dozens of popular breeds in our dog breeds directory.

For pregnant, breeding, or lactating dogs, NexGard has not been evaluated for safety, and its use in these populations is generally not recommended unless the veterinarian determines that the benefits outweigh the potential risks.

NexGard vs. Other Flea and Tick Preventatives

The flea and tick prevention market is crowded, and dog owners often wonder how NexGard compares to other available options. Here is how it stacks up against the most common alternatives.

NexGard vs. Bravecto. Both are oral isoxazoline-based chewables. The primary difference is duration: NexGard is administered monthly, while Bravecto lasts approximately 12 weeks. Some owners prefer the convenience of a quarterly dose; others prefer the monthly schedule because it is easier to remember as part of a routine. Efficacy against common flea and tick species is comparable.

NexGard vs. Simparica and Simparica Trio. Simparica is another monthly isoxazoline chewable with a similar mechanism of action. Simparica Trio adds protection against heartworm disease, roundworms, and hookworms, making it a broader-spectrum product. If your dog is not currently on heartworm prevention, a combination product like Simparica Trio may simplify your medication schedule.

NexGard vs. Frontline (topical). Frontline is a topical solution applied to the skin between the shoulder blades. It uses fipronil rather than an isoxazoline. Topicals can be a good option for dogs who have difficulty with oral medications or who have a history of neurological sensitivity. The trade-off is that topicals can be messy, may lose efficacy if the dog swims or bathes frequently, and require careful application to be effective.

NexGard vs. Seresto collar. The Seresto collar provides continuous flea and tick protection for up to eight months using imidacloprid and flumethrin. It is a convenient option for owners who prefer not to remember monthly dosing. However, the collar must remain in contact with the skin to work, and there have been reports of skin irritation at the collar site in some dogs. Collar-based protection also tends to be strongest around the neck and shoulders and may be slightly less effective at the extremities.

No single product is the right choice for every dog. The best preventative is the one your dog will tolerate, that covers the parasites relevant to your geographic area, and that fits your budget and schedule. Your veterinarian is the best resource for making that decision.

When to Start and How Long to Continue

Puppies can begin NexGard as early as eight weeks of age, provided they weigh at least four pounds. Starting early is important because puppies are especially vulnerable to flea infestations, which can cause anemia in very young or very small dogs due to blood loss. If you are bringing home a new puppy or a rescue dog of any age, flea and tick prevention should be one of the first conversations you have with your veterinarian. Our adoption resources can help you prepare for that first vet visit and beyond.

Flea and tick prevention should be continued year-round in most regions. While tick activity decreases in cold weather, it does not stop entirely — deer ticks, for instance, remain active at temperatures just above freezing. Fleas, meanwhile, thrive indoors regardless of the season. Stopping prevention during winter and restarting in spring creates a gap that parasites can exploit, and re-establishing control after a lapse can take months.

What NexGard Does Not Cover

It is important to understand the limits of any single medication. NexGard kills fleas and ticks only. It does not prevent heartworm disease, and it does not treat or prevent intestinal parasites such as roundworms, hookworms, whipworms, or tapeworms. Most dogs need a separate heartworm preventative given alongside their flea and tick protection, unless they are on a combination product that covers both.

If you are looking for simplified parasite coverage, ask your veterinarian about NexGard SPECTRA, which combines afoxolaner with milbemycin oxime to cover fleas, ticks, heartworm, and several intestinal worms in a single monthly chewable. Availability varies by region, so this may or may not be an option depending on where you live.

Frequently Asked Questions

Is NexGard safe for all dogs?

NexGard is FDA-approved for dogs and puppies eight weeks of age and older, weighing at least four pounds. It is safe for most dogs when used as directed. However, dogs with a history of seizures or neurological conditions should be evaluated individually by a veterinarian before starting NexGard, due to the rare potential for neurological side effects associated with isoxazoline drugs. It is not approved for cats and should never be given to them.

Can I give NexGard to my dog without a prescription?

No. NexGard is a prescription medication in the United States and most other countries. You will need a current veterinary-client-patient relationship and a valid prescription from your veterinarian to purchase it. This requirement exists because proper dosing depends on accurate weight measurement and a health assessment to ensure the product is appropriate for your individual dog.

What happens if I miss a monthly dose of NexGard?

If you miss a dose, give NexGard as soon as you remember and resume the regular monthly schedule from that date. A missed dose means your dog was unprotected during the gap, so check thoroughly for fleas and ticks, particularly if your dog spends time outdoors. If you find live parasites, consult your veterinarian about whether additional treatment is needed to address a potential infestation.

Does NexGard kill ticks already attached to my dog?

Yes. NexGard kills ticks that are already attached and feeding. After ingesting afoxolaner through the blood meal, attached ticks are typically killed within 48 hours. However, NexGard does not repel ticks, so you may still find live ticks on your dog before the medication takes full effect. Checking your dog after outdoor activity remains a good habit even when using a preventative.

Can NexGard be used alongside other medications?

NexGard has been used safely alongside many common veterinary medications, including heartworm preventatives, antibiotics, anti-inflammatories, and vaccines. No significant drug interactions have been identified in clinical studies. That said, always inform your veterinarian about all medications and supplements your dog is taking before starting any new treatment, including NexGard.

How should I store NexGard?

Store NexGard at room temperature, between 68 and 77 degrees Fahrenheit, in its original packaging. Keep it out of reach of children and pets — because the chew is flavored, dogs may attempt to eat additional tablets if they can access the package. If your dog accidentally consumes more than the prescribed dose, contact your veterinarian or an emergency animal poison hotline immediately.

Making the Right Choice for Your Dog

Flea and tick prevention is not optional — it is a core part of responsible dog ownership, right alongside proper nutrition, regular exercise, and routine veterinary care. NexGard for dogs has earned its place as one of the most trusted options available because it is effective, easy to administer, and backed by extensive clinical data. But no medication is one-size-fits-all. The right preventative for your dog depends on their health history, their lifestyle, the parasites common in your area, and what other medications they may need.

Talk to your veterinarian. Bring your questions. And if you are looking for a dog to share your life with, take a look at the dogs waiting for homes on our adoption page — every one of them deserves a life free from parasites and full of the care that comes with a loving home. You can also explore our dog breeds directory to learn about the health needs, temperaments, and care requirements of specific breeds before you decide which dog is the right fit for your family.