Constipation in Cats: Causes, Signs, and When It Becomes Serious
A constipated cat in the litter box looks a lot like a cat with a urinary problem — and the difference matters urgently. Here's how to tell, and what to do.
What you need to know
Constipation is significantly more common in cats than in dogs, and it has a wider range of potential severity — from a simple, easily managed episode to a chronic, progressive condition called obstipation or megacolon that can become debilitating without proper treatment.
One of the most critical — and potentially life-saving — things to understand as a cat owner is the difference between a cat straining to defecate and a cat straining to urinate. These look nearly identical in the litter box, but urinary obstruction in male cats is a life-threatening emergency requiring immediate care. Always err on the side of a vet visit when you're unsure.
If a male cat is repeatedly visiting the litter box and straining without producing urine, this is a urinary obstruction and a life-threatening emergency. Go to an emergency vet immediately — do not wait to see if it resolves. A blocked cat can die within 24–48 hours. If you are unsure whether your cat is straining to urinate or defecate, treat it as a urinary emergency until proven otherwise.
What is constipation in cats?
Constipation occurs when stool moves too slowly through the colon, allowing excessive water reabsorption. The result is hard, dry feces that are difficult or painful to pass. When stool accumulates and the colon becomes impacted, this is called obstipation. When the colon loses its ability to contract effectively after repeated stretching, the condition progresses to megacolon — a potentially irreversible dilation of the colon requiring long-term medical management or surgery.
Common causes of constipation in cats
- Dehydration — The most common contributing factor; cats are naturally poor water drinkers and many are chronically mildly dehydrated, especially on dry food diets
- Dietary factors — Low-fiber or low-moisture diets; inadequate water intake
- Hairballs — Can physically obstruct colonic transit in some cases
- Obesity — Reduces colonic motility and physical activity
- Orthopedic pain — Arthritis or hip pain making the litter box posture uncomfortable, leading to stool retention
- Pelvic abnormalities — Narrowed pelvic canal from old fractures reducing the space available for stool passage
- Neurological conditions — Nerve damage affecting colonic motility (e.g., Manx cats, spinal cord disease)
- Stress and litter box aversion — Cats that avoid the litter box retain stool, leading to constipation
- Chronic kidney disease — Causes systemic dehydration which worsens colonic water reabsorption
- Megacolon — Idiopathic megacolon (no identifiable cause) is unfortunately common in middle-aged male cats
Signs of constipation in cats
- Frequent trips to the litter box with little or no stool produced
- Straining, crouching, or vocalizing in the litter box
- Hard, dry, or very small stools — or no stool for more than 48 hours
- Blood-streaked stool from straining
- Reduced appetite or complete food refusal
- Lethargy or hiding
- Vomiting — constipated cats often vomit as a result of colonic distension and nausea
- A visibly distended or uncomfortable abdomen
How constipation is diagnosed
Your veterinarian will assess:
- Physical and rectal exam — Palpation of hard fecal material in the colon; assessment of rectal anatomy
- Abdominal radiographs — X-rays show the degree of fecal impaction and colonic dilation; essential for assessing severity and ruling out obstruction
- Bloodwork and urinalysis — To identify underlying causes such as CKD, electrolyte abnormalities, or dehydration
- Neurological assessment — If spinal or nerve involvement is suspected
Treatment options
Mild to moderate constipation
- Increased hydration — Transitioning to wet food, adding water to food, or using a pet water fountain significantly increases daily water intake
- Laxatives — Lactulose (osmotic laxative) is commonly prescribed; polyethylene glycol (MiraLAX) is used in some cats — always under veterinary guidance and at appropriate doses
- Fiber supplementation — Psyllium or canned pumpkin in small amounts may help some cats; discuss with your vet before adding
- Hairball remedies — May help if hairballs are a contributing factor
- Litter box management — Clean boxes, accessible locations, and appropriate litter type reduce avoidance behavior
Moderate to severe constipation / obstipation
- Manual decolonization (enema / manual extraction) — Performed under sedation or anesthesia by your veterinarian; not a home procedure
- IV fluid therapy — Corrects dehydration and helps soften impacted stool
- Prokinetics — Medications that stimulate colonic motility, such as cisapride (compounded)
Chronic / megacolon
- Long-term management with lactulose, cisapride, and dietary modification
- Subtotal colectomy — Surgical removal of the non-functional colon; often produces excellent outcomes in cats with true megacolon who have failed medical management; most cats do well post-surgically
- Increase moisture intake — Feed wet food as the primary diet, or add water or low-sodium broth to dry food; this is the single most impactful long-term change
- Maintain a healthy weight — Obesity significantly impairs colonic motility
- Keep litter boxes clean and accessible — One box per cat plus one, scooped daily; avoid covered boxes for cats prone to avoidance
- Manage pain — If your cat has arthritis, treating the pain may resolve litter box reluctance and reduce stool retention
- Regular grooming — Reduces hairball load, particularly in long-haired breeds
- Monitor frequency — Know your cat's normal defecation pattern so deviations are caught early
When to contact your veterinarian
- Your cat has not produced stool in 48–72 hours
- Your cat is straining repeatedly with nothing produced — rule out urinary obstruction first
- Your cat is vomiting alongside litter box straining
- Your cat is lethargic, hiding, or refusing food
- You see blood on or in the stool
- Your cat has a history of constipation and symptoms are returning
- You are considering any laxative — confirm type and dose with your vet before use; some human products are toxic to cats
Common myths
Myth: "I can give my cat a human laxative or enema at home"
This is genuinely dangerous. Several human laxative ingredients and enema solutions — including sodium phosphate enemas — are toxic to cats and can cause fatal electrolyte imbalances. Never administer a human enema or laxative to a cat without explicit veterinary instruction on a cat-safe product and dose. Manual decolonization should always be performed by a veterinarian under appropriate sedation.
Myth: "Once the constipation resolves it won't come back"
Cats that have experienced significant constipation or obstipation are at higher risk of recurrence, particularly if underlying causes (dehydration, obesity, pain) are not addressed. Megacolon, once established, does not resolve spontaneously and requires lifelong management. Prevention and early intervention are far more effective than repeated crisis management.
- Constipation is common in cats and can progress from manageable to serious — early intervention matters
- A cat straining in the litter box may be constipated or may have a urinary obstruction — if unsure, treat as an emergency
- Dehydration is the most common contributing factor — increasing moisture intake is the most impactful preventive step
- Never give a human laxative or enema to a cat without explicit veterinary guidance — some are toxic
- Repeated constipation can lead to megacolon — a progressive condition requiring long-term management or surgery
- Wet food as the primary diet significantly reduces constipation risk in cats
- Arthritis pain causing litter box avoidance is an underrecognized driver of constipation in older cats
- Washabau RJ, Hasler AH. Constipation, obstipation, and megacolon. In: August JR, ed. Consultations in Feline Internal Medicine. Vol 3. WB Saunders; 1997:104–112.
- Trevail T, Gunn-Moore D, Carrera I, Courcier E, Sullivan M. Radiographic diameter of the colon in normal and constipated cats and in cats with megacolon. Veterinary Radiology & Ultrasound. 2011;52(5):516–520. doi.org/10.1111/j.1740-8261.2011.01836.x
- Rohrer CR, et al. Efficacy of lactulose in the management of chronic idiopathic large bowel constipation in cats. Journal of the American Animal Hospital Association. 1993;29:122–125.
- Freiche V, Houston D, Weese H, et al. Uncontrolled study assessing the impact of a psyllium-enriched extruded dry diet on faecal consistency in cats with constipation. Journal of Feline Medicine and Surgery. 2011;13(12):903–911. doi.org/10.1016/j.jfms.2011.07.013
- Bertoy RW. Megacolon in the cat. Veterinary Clinics of North America: Small Animal Practice. 2002;32(4):901–915. doi.org/10.1016/S0195-5616(02)00022-4
Last reviewed by PetGutHealth: June 2026
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Content on PetGutHealth is for educational purposes only and is not veterinary medical advice. Always consult your veterinarian regarding your pet's health.