Why Is My Dog Throwing Up Blood?

Seeing blood when a dog vomits is alarming and can come from different body systems; identifying the likely source and severity helps guide what to do next.

Understanding the Symptom: Hematemesis vs. Other Blood

“Vomiting blood” (hematemesis) specifically means blood is coming up from the upper gastrointestinal tract, but owners often misinterpret blood that actually originates in the nose, mouth, or lungs. Bright red blood mixed with vomit usually indicates recent, active bleeding from the mouth, esophagus, or stomach, while dark, granular “coffee‑ground” material suggests blood that has been exposed to gastric acid for at least 2 hours^[1].

Examining where the blood is most concentrated (e.g., on bedding versus on the muzzle) and whether coughing or sneezing precedes the event helps distinguish swallowed nasal/oral bleeding from true hematemesis^[1].

Immediate Danger Signs and When to Seek Emergency Care

• Pale or gray gums, prolonged capillary refill time over 2 seconds, weak pulses, or collapse are signs of shock and require immediate emergency care^[2].
• Persistent vomiting of blood—more than 2 episodes in a few hours—or bright red ongoing hemorrhage warrants urgent veterinary evaluation^[2].
• Significant blood loss causing lethargy or rapid breathing should prompt transport to an emergency facility, as transfusion or intensive care may be needed^[2].

Because the amount of visible blood can underestimate internal loss, clinicians use vital signs and laboratory data rather than only owner-observed volume to judge urgency^[2].

Gastrointestinal Causes (Ulcers, Gastritis, Infections, Parasites, Foreign Bodies, Tumors)

Primary GI causes of hematemesis include gastric or duodenal ulcers, erosive gastritis, severe bacterial or viral enteritis, parasitic infestations, ingested foreign bodies that abrade the mucosa, and neoplasia of the stomach. Peptic ulcers and erosive gastritis are common culprits when a dog has known NSAID exposure or stress-related mucosal damage^[3].

Parasitic disease such as heavy hookworm burdens can cause melena and overt GI bleeding; in severe infestations packed cell volume (PCV) can drop below 20% from chronic blood loss^[3].

Foreign bodies that lodge in the stomach or cause focal ischemia can produce recurrent hematemesis and may be visualized on imaging or found by endoscopy; gastric tumors may cause intermittent bleeding that becomes progressive over weeks to months^[3].

Common GI causes, typical clues, and diagnostic priorities

Cause	Clues	Key Test	Usual Urgency
Peptic ulcer	NSAID history, melena	Endoscopy/upper GI imaging	High
Hookworms	Young dog, dark stool	Fecal exam/antigen testing	Moderate
Foreign body	Acute vomiting, radiopaque item	X‑ray/ultrasound	High
Gastric tumor	Chronic intermittent bleed, weight loss	Endoscopy/biopsy	Variable

Systemic and Coagulation Disorders

Non-GI diseases can cause bleeding into the GI tract by altering clotting. Rodenticide exposure and other toxins that inhibit vitamin K–dependent clotting factors can produce GI hemorrhage as the first obvious sign, often before external bleeding is noted^[4].

Liver failure impairs clotting factor production and may present with GI bleeding; baseline coagulation testing such as PT and aPTT, and platelet counts are essential when systemic disease is suspected^[4].

Respiratory, Oral and Trauma-Related Sources

Bleeding from the nose (epistaxis), oral cavity (dental disease or tongue injuries), or lungs (hemoptysis) can be swallowed and later appear as bloody vomit. Recurrent coughing or nasal discharge before the event often points to a respiratory origin, while blood localized to the mouth or dental sockets suggests oral trauma or dental disease^[1].

Detailed physical exam focusing on the oral cavity, nasal passages, and thorax helps separate these non-GI sources from true hematemesis^[1].

Toxins and Medications

Anticoagulant rodenticides often produce bleeding within 2–7 days of ingestion because preformed liver clotting factors need to be depleted before hemorrhage appears^[5].

NSAIDs and some human medications can cause erosive gastritis and ulcers; even single high-dose exposures or repeated therapeutic dosing in sensitive dogs may lead to bleeding within 24–72 hours depending on the drug and dose^[5].

Household toxins, certain plants, and illicit substances may also cause direct mucosal damage or coagulopathy and should be considered when owner history suggests possible access to these agents^[5].

Diagnostic Workup: Tests and Procedures the Vet Will Use

Initial assessment begins with a focused physical exam and vital signs, followed by a complete blood count (CBC) and chemistry panel; a CBC can reveal anemia or a left shift that supports infection or systemic inflammation^[2].

Coagulation testing (PT, aPTT) and platelet count are standard when bleeding is present; prolongation of PT or aPTT by more than 25% compared with reference ranges indicates a clinically relevant coagulopathy that requires correction^[2].

Fecal testing for occult blood and parasites, abdominal radiographs and ultrasound to look for foreign bodies or masses, and endoscopy (when available) to visualize and potentially biopsy gastric lesions form the next steps in a stepwise diagnostic plan^[3].

Stabilization and Emergency Treatment

Immediate management focuses on stabilizing circulation and stopping ongoing blood loss. Initial fluid resuscitation often uses isotonic crystalloids at bolus doses tailored to the dog’s size and perfusion, followed by monitoring and maintenance fluids; a guideline maintenance rate is roughly 60 mL/kg/day for many adult dogs, adjusted for age and condition^[4].

Blood transfusion is considered when PCV is critically low (often <20%–25% depending on clinical signs) or when there is ongoing hemorrhage despite fluids; transfusion decisions balance PCV, clinical perfusion, and underlying cause^[4].

Other emergency measures include antiemetics to control vomiting, proton‑pump inhibitors or H2 blockers to reduce gastric acidity and limit further mucosal damage, and gastroprotectants such as sucralfate when indicated by endoscopy or clinical suspicion of erosive disease^[3].

Definitive Treatments and Surgical Indications

Targeted therapy depends on the diagnosis: antiparasitics for hookworm or other worms, antibiotics for confirmed bacterial enteritis, and specific antidotes such as vitamin K1 for anticoagulant rodenticide exposure. Vitamin K1 therapy is typically continued for 2–4 weeks for second‑generation anticoagulant ingestion based on toxin and response to therapy^[5].

Endoscopic intervention can remove some foreign bodies or allow targeted biopsies and localized hemostasis; surgical exploration is indicated when a foreign body is not retrievable endoscopically, when there is gastrointestinal perforation, or when a mass requires excision for diagnosis and treatment^[3].

Home Care, Prognosis, and Follow‑Up Monitoring

Recovery timelines vary by cause: toxin‑related coagulopathies often improve within days of antidotal therapy but require repeat clotting tests during and after therapy; uncomplicated gastritis may resolve in 48–72 hours with supportive care, while neoplasia or major surgical recovery may require weeks to months of monitoring and adjuvant treatment^[2].

Owners should watch for recurrent vomiting, melena, weakness, or pallor and seek recheck care if any of these recur; scheduled rechecks often include repeat CBC and clotting times 24–72 hours after stabilization and additional imaging or endoscopy as guided by clinical response^[2].

Practical Monitoring and Medication Details

When a dog is hospitalized for GI bleeding, frequent reassessment of perfusion and laboratory values guides ongoing care. Repeating a packed cell volume/hematocrit and total solids at 6–12 hour intervals during active bleeding is a common practice until stability is achieved^[2].

Fluid therapy begins with bolus resuscitation when indicated; a common isotonic crystalloid bolus is 10–20 mL/kg given over 10–20 minutes for hypovolemic dogs, with reassessment after each bolus^[4].

After initial resuscitation, a typical maintenance fluid guideline used by clinicians is approximately 60 mL/kg/day, expressed in clinical terms as mL/kg/day for accurate weight‑based dosing^[4].

For example, a 50 lb (22.7 kg) dog receiving 60 mL/kg/day requires about 1,362 mL/day of fluids, which is just under 5.7 cups (1 cup = 240 mL) when converted for home measures^[4].

Blood product dosing follows transfusion principles: a unit dose of packed red blood cells often used in dogs is approximately 10 mL/kg, which typically raises PCV by about 4%–6% depending on the product and recipient volume status^[2].

When anticoagulant rodenticide is suspected, vitamin K1 dosing and monitoring are critical; commonly used oral vitamin K1 protocols continue for 2–4 weeks depending on the specific rodenticide and toxin assay results, with coagulation reassessment 48–72 hours after initiating therapy^[5].

Medications and Duration Considerations

Acid suppression and mucosal protectants are standard when erosive gastritis or ulcers are suspected: proton‑pump inhibitors such as omeprazole are often dosed at 0.7–1 mg/kg once or twice daily, with treatment courses commonly extending at least 7–14 days for uncomplicated ulcers^[3].

Sucralfate given at 0.5–1 g per dog every 8 hours provides a protective barrier and is frequently continued for 7–14 days alongside acid suppression when endoscopy or clinical signs support mucosal erosion^[3].

Antiemetics (for example maropitant) are used to control vomiting in the hospitalized dog; a typical maropitant dose is 1 mg/kg once daily for several days depending on response, and antiemetic therapy is continued until vomiting resolves and oral intake is stable^[3].

Common Outcomes by Cause

Recovery timelines differ by diagnosis: uncomplicated acute gastritis or ingestion-related vomiting often resolves in 24–72 hours with supportive care, including antiemetics and brief dietary modification^[3].

Parasitic causes treated with appropriate anthelmintic therapy typically show clinical improvement within 48–72 hours, although severe anemia from chronic hookworm infestation may require weeks to correct and repeated deworming and rechecks^[3].

Toxin-induced coagulopathies generally require a longer monitoring window: with vitamin K1 therapy for warfarin‑type rodenticides, coagulation tests are usually checked every 48–72 hours during the first week and again before stopping therapy around 2–4 weeks to confirm sustained normal clotting times^[5].

Dogs undergoing endoscopic removal of a gastric foreign body often recover quickly and may be discharged within 24–48 hours if no complications are found, whereas surgical enterotomy or gastrotomy carries a longer hospitalization and recovery period typically measured in 7–14 days for incision healing and activity restriction^[3].

When to Contact Your Veterinarian Immediately After Discharge

After discharge, owners should contact their veterinarian promptly if the dog has recurrent vomiting of blood, dark tarry stools, weakness, fainting, or pale gums; any single episode of collapse or seizure requires immediate emergency attention^[2].

Recheck laboratory testing such as CBC or coagulation profiles is commonly scheduled at 24–72 hours post‑discharge for cases involving transfusion, coagulopathy, or significant anemia, and earlier testing is performed if clinical signs worsen^[2].

Long-Term Monitoring and Preventing Recurrence

For dogs with medication‑induced or toxin‑induced ulcers, avoiding the offending drug and using gastroprotective strategies during future NSAID therapy reduces recurrence risk; many clinicians recommend using the lowest effective NSAID dose and concurrent gastroprotection in dogs with prior GI ulceration^[5].

Dogs that required surgery for foreign body removal or tumor excision typically have post‑op rechecks at 7–14 days to assess incision healing and at 4–6 weeks to evaluate clinical recovery and plan any adjunct therapies based on histopathology results^[3].

Chronic conditions that predispose to GI bleeding, such as liver disease or clotting disorders, often need lifelong monitoring; routine intervals for CBC and chemistry screening are commonly every 3–6 months or as advised by the attending clinician based on disease severity and stability^[2].

Practical Owner Tips for the Immediate Home Period

Provide small, frequent bland meals once vomiting has ceased—many clinicians advise starting with 1/4 to 1/3 of the dog’s normal meal size every 4–6 hours for the first 24–48 hours, gradually increasing as tolerated over 2–3 days^[3].

Avoid giving over‑the‑counter human medications such as NSAIDs unless explicitly prescribed by the veterinarian, because even a single inappropriate dose can precipitate or worsen GI ulceration and bleeding^[5].

Keep a close eye on hydration by monitoring skin turgor and gum moisture; if the dog has decreased drinking or shows signs of persistent dehydration, contact the clinic because outpatient oral fluids may be insufficient and IV therapy could be needed^[4].

Sources

• merckvetmanual.com — Merck Veterinary Manual.
• avma.org — American Veterinary Medical Association.
• vcahospitals.com — VCA Animal Hospitals clinical resources.
• aspca.org — ASPCA Animal Poison Control and toxicology resources.
• wsava.org — World Small Animal Veterinary Association guidelines.