How Much Amoxicillin for Dogs: Dosage Guide by Weight & Condition
Learn how much amoxicillin for dogs is safe by weight and condition. Covers dosage ranges, side effects, drug interactions, and when to call your vet.
Amoxicillin requires a veterinarian prescription and should only be used under direct veterinary supervision. Never administer human amoxicillin or leftover prescriptions to your dog without explicit veterinary instruction. Incorrect dosing can cause treatment failure, antibiotic resistance, or serious adverse reactions.
What Is Amoxicillin and What Is It Used for in Dogs?
Amoxicillin is a broad-spectrum aminopenicillin antibiotic belonging to the beta-lactam drug class. It is one of the most commonly prescribed antibiotics in veterinary medicine due to its effectiveness against a wide range of bacterial infections and its relatively favorable safety profile in dogs.
How Amoxicillin Works (Mechanism of Action)
Amoxicillin kills bacteria by inhibiting the synthesis of their cell walls. Specifically, it binds to penicillin-binding proteins (PBPs) located on the inner surface of the bacterial cell membrane. This binding prevents the cross-linking of peptidoglycan chains — the structural scaffolding that gives bacterial cell walls their strength. Without a properly formed cell wall, bacteria absorb water, swell, and burst (lysis). Because amoxicillin targets a structure unique to bacteria, it does not harm your dog's own cells.
Amoxicillin is bactericidal (it kills bacteria outright) rather than bacteriostatic (merely slowing growth), and it is most effective against actively dividing organisms. It has good activity against many Gram-positive bacteria (including Streptococcus and some Staphylococcus species) and several Gram-negative bacteria (including E. coli, Proteus, and Salmonella). However, it is destroyed by beta-lactamase enzymes produced by some resistant bacteria — which is why your vet may prescribe amoxicillin-clavulanate (Clavamox) instead for those infections.
FDA-Approved Veterinary Uses
The FDA has approved amoxicillin for use in dogs specifically for the treatment of infections caused by susceptible strains of bacteria. According to the Merck Veterinary Manual, approved indications include:
- Skin and soft tissue infections — wounds, abscesses, cellulitis, pyoderma
- Urinary tract infections (UTIs) — cystitis caused by susceptible organisms
- Respiratory tract infections — bacterial pneumonia, bronchitis
- Gastrointestinal infections — bacterial enteritis
Common Off-Label Uses
Veterinarians frequently prescribe amoxicillin off-label for conditions not listed on the FDA label but supported by clinical experience and veterinary literature:
- Dental infections — periodontal disease, tooth root abscesses
- Otitis media — middle ear infections (often combined with other treatments)
- Prophylactic use — pre-surgical antibiotic coverage in certain procedures
- Leptospirosis — as part of a broader treatment protocol (though doxycycline is preferred)
- Bone infections (osteomyelitis) — when culture results confirm susceptibility
How Much Amoxicillin for Dogs: Dosage by Weight and Condition
The question "how much amoxicillin for dogs" does not have a single answer — the correct dose depends on your dog's weight, the type and severity of infection, kidney function, and the specific amoxicillin formulation your vet prescribes. Below are the standard veterinary dosage ranges used in clinical practice.
| Condition | Dose (mg/kg) | Dose (mg/lb) | Frequency | Typical Duration |
|---|---|---|---|---|
| Skin & soft tissue infections | 10–20 mg/kg | 5–9 mg/lb | Every 12 hours | 7–14 days |
| Urinary tract infections | 10–20 mg/kg | 5–9 mg/lb | Every 12 hours | 10–14 days |
| Respiratory infections | 10–20 mg/kg | 5–9 mg/lb | Every 12 hours | 10–21 days |
| Dental infections | 12–22 mg/kg | 5.5–10 mg/lb | Every 12 hours | 7–10 days |
| Severe/systemic infections | 20–40 mg/kg | 9–18 mg/lb | Every 8 hours | 14–28+ days |
Practical Dosage Examples by Dog Weight
To make this concrete, here is how a standard dose of 10 mg/kg every 12 hours translates for common dog weights:
| Dog Weight | Dose per Administration (10 mg/kg) | Daily Total | Common Tablet Size Used |
|---|---|---|---|
| 10 lb (4.5 kg) | 45 mg | 90 mg/day | 50 mg tablet (approx. 1 tab) |
| 25 lb (11.3 kg) | 113 mg | 226 mg/day | 125 mg tablet (approx. 1 tab) |
| 50 lb (22.7 kg) | 227 mg | 454 mg/day | 250 mg tablet (approx. 1 tab) |
| 75 lb (34 kg) | 340 mg | 680 mg/day | 250 mg + 125 mg tablets |
| 100 lb (45.4 kg) | 454 mg | 908 mg/day | 500 mg tablet (approx. 1 tab) |
Critical note: These are reference calculations only. Your veterinarian determines the exact dose for your dog based on clinical assessment, culture results, and individual health factors. Never adjust the dose on your own.
Administration Instructions: How to Give Amoxicillin to Your Dog
Amoxicillin for dogs comes in several formulations, and how you give it matters for both effectiveness and compliance:
Available Formulations
- Oral tablets — 125 mg, 250 mg, 500 mg (most common; scored for splitting)
- Chewable tablets — flavored (beef or liver), easier for dogs that resist pilling
- Oral suspension — liquid form, typically 50 mg/mL or 125 mg/mL; ideal for small dogs and puppies
- Injectable (SQ, IM, IV) — administered in-clinic for severe infections or dogs that cannot take oral medication
With or Without Food?
Amoxicillin can be given with or without food. However, if your dog experiences nausea or vomiting on an empty stomach, giving the dose with a small meal typically resolves this. Unlike some antibiotics (e.g., doxycycline), food does not significantly reduce amoxicillin absorption. For the chewable formulation, most dogs accept it readily as a treat.
Duration: How Long Does My Dog Need to Be on Amoxicillin?
This depends entirely on the infection type and severity, but here are general veterinary guidelines:
- Uncomplicated skin infections: 7–14 days
- UTIs: 10–14 days (with a follow-up urinalysis to confirm clearance)
- Respiratory infections: 10–21 days, continuing at least 7 days past clinical resolution
- Dental infections: 7–10 days, often paired with dental procedure
- Deep or chronic infections (osteomyelitis, deep pyoderma): 4–8 weeks or longer
A common mistake owners make is stopping antibiotics early because the dog "looks better." According to the AVMA's antimicrobial use guidelines, prematurely stopping antibiotics is a primary driver of antibiotic-resistant bacteria. Always complete the full course your vet prescribes, even if symptoms resolve within 2–3 days.
Side Effects of Amoxicillin in Dogs
Amoxicillin is generally well-tolerated, but like all medications, it can cause side effects. Most are mild and self-limiting. Understanding the frequency and severity helps you know what is expected versus what warrants a call to your vet.
| Side Effect | Estimated Frequency | Severity | What to Do |
|---|---|---|---|
| Vomiting | ~10–15% | Mild | Give with food; contact vet if persistent |
| Diarrhea / loose stools | ~10–20% | Mild to Moderate | Add probiotic; monitor; call vet if bloody or >48 hrs |
| Decreased appetite | ~5–10% | Mild | Offer food with dose; usually resolves |
| Drooling (oral suspension) | ~5% | Mild | Mix with small amount of food; try chewable instead |
| Allergic reaction (hives, facial swelling) | <1–2% | Serious | Stop medication; contact vet immediately |
| Anaphylaxis (collapse, difficulty breathing) | <0.1% | Emergency | Emergency vet visit immediately |
| Severe bloody diarrhea (C. difficile overgrowth) | Rare | Serious | Contact vet; may need to discontinue |
🚨 When to Call Your Vet Immediately
Stop giving amoxicillin and contact your veterinarian or an emergency clinic right away if your dog shows any of these signs:
- Facial swelling, hives, or widespread itching (possible allergic reaction)
- Difficulty breathing, wheezing, or collapse (anaphylaxis)
- Severe or bloody diarrhea, especially with lethargy
- Seizures (rare, but reported at very high doses or in dogs with kidney impairment)
- Vomiting that prevents keeping the medication down for more than one dose
If you suspect a severe allergic reaction outside of clinic hours, you can also contact the ASPCA Animal Poison Control Center at (888) 426-4435 (24/7, consultation fee applies) for guidance.
Contraindications: Which Dogs Should NOT Receive Amoxicillin
While amoxicillin is safe for most dogs, certain animals should not receive it or require modified dosing under close veterinary monitoring:
- Known penicillin or cephalosporin allergy: Dogs that have previously reacted to any penicillin-family drug (ampicillin, penicillin G, amoxicillin-clavulanate) or cephalosporins (cephalexin, cefpodoxime) are at high risk for cross-reactive allergic responses. This is an absolute contraindication.
- Severe kidney disease: Amoxicillin is primarily excreted through the kidneys. Dogs with significantly impaired renal function (IRIS Stage 3–4 kidney disease) may accumulate toxic drug levels. Your vet will either reduce the dose, extend the dosing interval, or select an alternative antibiotic.
- History of antibiotic-associated colitis: Dogs with prior episodes of Clostridioides difficile overgrowth from antibiotic use may be at elevated risk of recurrence.
- Neonatal puppies: Very young puppies (under 4 weeks) have immature kidney function. Dosing must be adjusted by a veterinarian, and alternative antibiotics may be preferred.
- Small herbivores in multi-pet households: While not a dog contraindication, be aware that amoxicillin is extremely dangerous to rabbits, guinea pigs, and hamsters. Keep all medication secured away from other household pets.
Drug Interactions with Amoxicillin
Always tell your veterinarian about every medication, supplement, and over-the-counter product your dog is taking before starting amoxicillin. Known interactions include:
| Drug/Supplement | Interaction Type | Clinical Significance |
|---|---|---|
| Bacteriostatic antibiotics (tetracyclines, chloramphenicol, macrolides) | Antagonistic — bacteriostatic drugs slow bacterial growth, reducing amoxicillin's effectiveness (which requires actively dividing cells) | Moderate to High — avoid combining unless specifically directed by a veterinarian |
| Methotrexate | Amoxicillin reduces renal clearance of methotrexate, increasing toxicity risk | High — dose adjustment or alternative antibiotic required |
| Probenecid | Blocks renal tubular secretion of amoxicillin, increasing blood levels | Moderate — sometimes used intentionally to extend antibiotic levels |
| Aminoglycosides (gentamicin, amikacin) | Amoxicillin can inactivate aminoglycosides if mixed in the same syringe/IV line; in vivo, they may have synergistic effects | Moderate — must be administered separately if both are prescribed |
| Oral bacterin vaccines (e.g., leptospirosis oral vaccines) | Antibiotics may reduce efficacy of live bacterial vaccines | Low to Moderate — timing separation recommended |
| Probiotics | Amoxicillin kills probiotic bacteria if given simultaneously | Low — separate administration by 2–3 hours |
Monitoring Requirements and Follow-Up
Depending on the infection type and your dog's health status, your veterinarian may recommend the following monitoring during amoxicillin treatment:
| Scenario | Monitoring Action | Timing | Estimated Cost |
|---|---|---|---|
| All infections | Clinical recheck — physical exam, symptom review | 5–7 days after starting | $50–$85 |
| UTIs | Urinalysis + urine culture to confirm bacterial clearance | 5–7 days after completing course | $80–$180 |
| Recurrent or deep infections | Bacterial culture & sensitivity (C&S) before and/or during treatment | Before starting; again if no improvement at 5–7 days | $120–$250 |
| Dogs with kidney disease | Serum biochemistry panel (BUN, creatinine, SDMA) | Baseline before treatment; recheck at 7–14 days | $100–$200 |
| Long-term courses (>4 weeks) | CBC + chemistry panel to monitor for bone marrow or organ effects | Every 2–4 weeks during treatment | $150–$280 |
Cost of Amoxicillin for Dogs
Amoxicillin is one of the most affordable veterinary antibiotics, and generic versions are widely available. Here is what you can expect to pay in 2026:
- Generic amoxicillin tablets (per 30-day supply): $8–$30 depending on dosage strength and pharmacy
- Veterinary-branded amoxicillin (e.g., Amoxi-Tabs, Amoxi-Drop): $15–$45 per course
- Oral suspension (liquid): $15–$35 per bottle
- Injectable (in-clinic administration): $25–$60 per dose, plus exam fee
Many veterinary clinics stock amoxicillin in-house and will dispense it directly. You can also ask for a written prescription to fill at a human pharmacy (CVS, Walgreens, Costco) or an online veterinary pharmacy (Chewy Pharmacy, 1-800-PetMeds). Generic human amoxicillin is often identical to the veterinary formulation and significantly cheaper — but only use it if your vet has prescribed that specific formulation and dose. Human amoxicillin suspensions may contain xylitol as a sweetener in some formulations, which is highly toxic to dogs.
Missed Dose and Overdose: What to Do
If You Miss a Dose
Give the missed dose as soon as you remember. However, if it is almost time for the next scheduled dose, skip the missed dose and continue with the regular schedule. Never double the dose to make up for a missed one. Consistently missing doses reduces treatment effectiveness and promotes antibiotic resistance — set phone reminders or use a pill organizer to stay on track.
If an Overdose Occurs
Amoxicillin has a wide safety margin in dogs, and mild overdoses (up to 2–3× the prescribed dose) typically cause only gastrointestinal upset — vomiting, diarrhea, and drooling. However, massive overdoses can lead to:
- Crystal formation in the urine (crystalluria), particularly in dehydrated dogs
- Neurological signs including tremors or seizures (very rare, usually with extreme overdoses)
- Severe electrolyte imbalances
If your dog ingests significantly more than the prescribed dose, contact your veterinarian or the ASPCA Animal Poison Control Center at (888) 426-4435 (24/7, consultation fee applies) immediately. Bring the medication bottle or packaging with you to the clinic so the veterinary team can confirm the exact formulation and strength ingested.
Alternatives to Amoxicillin for Dogs
If your dog cannot take amoxicillin — due to allergy, resistance, or lack of clinical response — your veterinarian may consider these alternatives:
| Alternative Antibiotic | Drug Class | When It's Preferred | Cost Range (30 days) |
|---|---|---|---|
| Amoxicillin-clavulanate (Clavamox) | Aminopenicillin + beta-lactamase inhibitor | Beta-lactamase-producing bacteria; resistant skin infections | $25–$65 |
| Cephalexin | First-generation cephalosporin | Skin infections; penicillin-allergic dogs (with caution for cross-reactivity) | $10–$35 |
| Doxycycline | Tetracycline | Tick-borne diseases, respiratory infections, leptospirosis | $15–$40 |
| Enrofloxacin (Baytril) | Fluoroquinolone | Gram-negative UTIs, prostatitis, deep infections | $20–$60 |
| Metronidazole | Nitroimidazole | Anaerobic infections, Giardia, inflammatory bowel disease | $10–$30 |
Your vet's choice of alternative depends on the suspected or confirmed bacteria, culture and sensitivity results, your dog's health history, and the infection site. Never switch antibiotics on your own — incomplete or inappropriate treatment can make infections harder to resolve.
Frequently Asked Questions
Can I give my dog human amoxicillin?
Technically, generic human amoxicillin and veterinary amoxicillin contain the same active ingredient. However, you should only give your dog amoxicillin that has been specifically prescribed for them by a veterinarian — at the exact dose and formulation they recommend. Human liquid amoxicillin may contain xylitol (toxic to dogs), and tablet strengths may not allow accurate dosing for your dog's weight. Using leftover human antibiotics is risky and illegal in some jurisdictions without a valid prescription.
How quickly does amoxicillin start working in dogs?
Most dogs begin showing improvement within 24–48 hours of starting amoxicillin. The antibiotic reaches peak blood concentrations within 1–2 hours of oral administration. However, visible improvement depends on the infection type — skin infections may take 3–5 days to show obvious change, while UTIs often improve within 24 hours. If your dog has not improved after 48–72 hours, contact your vet — the bacteria may be resistant, or the diagnosis may need reassessment.
Can amoxicillin cause diarrhea in dogs, and what should I do?
Yes, diarrhea is one of the most common side effects (affecting roughly 10–20% of dogs). Amoxicillin disrupts the normal gut microbiome alongside pathogenic bacteria. To help: give the medication with food, add a canine-specific probiotic (such as FortiFlora or Proviable) separated from the antibiotic dose by 2–3 hours, and ensure access to fresh water. If diarrhea becomes bloody, is accompanied by vomiting or lethargy, or persists beyond 48 hours, contact your veterinarian.
Is amoxicillin safe for pregnant or nursing dogs?
Amoxicillin is generally considered one of the safer antibiotics during canine pregnancy (classified as relatively low risk). However, any medication use during pregnancy should be explicitly approved by your veterinarian, who will weigh the risks of the infection against the risks of treatment. Amoxicillin does pass into milk in small amounts, so nursing puppies should be monitored for diarrhea.
What happens if I stop amoxicillin early because my dog seems better?
Stopping antibiotics prematurely is one of the most common and consequential mistakes pet owners make. Even when symptoms resolve, some bacteria may survive. These survivors are often the most resistant organisms, and they can multiply into a new infection that is harder to treat. The FDA warns that incomplete antibiotic courses contribute to the growing crisis of antimicrobial resistance. Always complete the full prescribed course and attend follow-up rechecks.
How should I store amoxicillin for my dog?
Tablets and capsules should be stored at room temperature (68–77°F / 20–25°C) in a dry place, away from direct sunlight and moisture. Oral suspension, once reconstituted, must be refrigerated (36–46°F / 2–8°C) and discarded after 14 days, as it loses potency. Never use expired amoxicillin — degraded antibiotics may be ineffective or, in the case of tetracycline-class drugs, potentially toxic (though this specific concern does not apply to amoxicillin, expired medication still loses efficacy).
This article is for informational purposes only and does not replace professional veterinary advice. Always consult your veterinarian before starting, stopping, or adjusting any medication for your dog. Individual treatment decisions should be made by a licensed veterinarian who has examined your animal.
Beth Carrasco
All our authors care for dogs every day — read more of their work on the authors page.
