Fiber for Cats: Psyllium 1-2 g, Pumpkin 1 tsp per 5 kg

Fiber is the cheapest fix for both constipation and diarrhea, and the two problems need opposite fibers. Constipation wants insoluble bulk plus water; diarrhea wants soluble gel that slows transit. The working doses are small: psyllium 1 to 2 g a day, plain canned pumpkin 1 teaspoon per 5 kg of body weight, always with 10 to 45 ml of extra water mixed in. Get the direction wrong and you turn a soft stool into a blockage or a hard stool into a waterfall.

Two problems, opposite fibers

Soluble fiber (psyllium, guar gum, pectin) dissolves into a gel. It holds water in the gut, ferments into short-chain fatty acids that feed colon cells, and slows transit, which is why it firms loose stool. Insoluble fiber (wheat bran, cellulose, pumpkin pulp) does not dissolve. It adds bulk, stretches the colon wall, and speeds transit, which is why it helps a colon that has gone lazy. A cat with hard, dry stool needs the second. A cat with cow-pie stool needs the first. A cat with hard stool followed by soft stool needs both, and that is where a 50/50 mix earns its place.

Doses that hold up

Fiber	Type	Fiber per day, low (g)	Fiber per day, high (g)	Water (ml)	Best for	Full effect (h)
Psyllium husk	Soluble, gel-forming	1	2	35	Diarrhea first, constipation second	36
Plain canned pumpkin	Mixed, mostly insoluble	4	8	12	Constipation, hairball stool	72
Wheat bran	Insoluble	2	3	25	Constipation only	96
Guar gum	Soluble	0.5	1	20	Diarrhea, colitis	36
Pumpkin plus psyllium, 50/50	Mixed	2	6.5	30	Hard stool with soft tail	48

The gram columns are the dose; the kitchen conversions are 1 level teaspoon of psyllium husk at about 2 g and 1 teaspoon of plain pumpkin at about 4 g, which is why 1 tsp per 5 kg lands at 4 g. Weigh the powder once on a kitchen scale and mark that scoop, because 1 teaspoon of one brand can weigh 1.5 g and another 3 g. Start at half the listed dose for 3 days: a 5 kg cat starts at 0.5 g of psyllium or 1/2 tsp of pumpkin, then goes up. Fiber given at full dose on day 1 produces gas, bloating, and a cat that refuses the bowl for a week.

The ratio is the whole trick

Think in percentages of total fiber, not in teaspoons. For diarrhea, aim at roughly 70 percent soluble to 30 percent insoluble: 1.5 g psyllium with 0.5 g pumpkin. For constipation, flip it: 30 percent soluble to 70 percent insoluble, so 0.5 g psyllium with 2 g pumpkin or bran. For a cat with both problems on alternate days, 50/50 and a stool log decides which way to push after 7 days. Getting the ratio backwards is the single most common reason home fiber fails: soluble fiber alone in a dehydrated cat turns into a plug, and insoluble fiber alone in an inflamed colon makes the diarrhea sharper.

Water is the actual medicine

Psyllium absorbs 10 to 15 times its weight in water. Give 1 g of it dry and the gel forms inside the colon by pulling water out of the stool, which makes hard stool harder. Every gram needs 10 to 15 ml of water alongside, mixed into wet food or given by syringe in 3 small aliquots. A 5 kg cat needs 200 to 300 ml of water a day in total (40 to 60 ml per kg), and most dry-fed cats run 50 to 100 ml short of that. Two changes fix the gap faster than any powder: move to a wet food that is 75 to 80 percent moisture, and add a water fountain. Fiber without that water is a constipation treatment that causes constipation.

The 7-day ramp

Days 1 to 3: one quarter of the target dose, mixed into 20 g of wet food, once a day. Days 4 and 5: half dose, split into 2 meals. Days 6 and 7: full dose, still split, because 2 small doses irritate the gut less than 1 large one. If the cat walks away from the bowl, drop back one step and hold it for 4 days rather than pushing. A food transition and a fiber increase at the same time is 2 variables at once, so add fiber first, wait 7 days, then change the food.

Where fiber backfires

Four situations need a vet before a scoop. A cat that has not passed stool for 48 hours may have an obstruction or a megacolon that bulk will worsen. A cat that is vomiting, off food, or losing weight is not a fiber case. A cat with a tense, painful abdomen should not be given bulk at all. And a cat with diabetes should get 100 percent pumpkin, never pumpkin pie filling: plain canned pumpkin runs about 7 g of carbohydrate per 100 g, while the pie filling runs 30 g or more per 100 g and can push a borderline cat into a glucose spike. For a cat on a low-carb diet, check the total carbohydrate load before adding anything.

Judging it in 14 days

Use a fecal score of 1 to 7, where 1 is hard pellets and 7 is water. The target is 3 or 4: formed, moist, picks up cleanly. Score every stool for 14 days and write down 3 things per entry: date, score, and whether straining lasted more or less than 2 minutes. Fiber for constipation should move the score 1 to 2 points in 4 to 7 days; fiber for diarrhea should move it in 24 to 72 hours. If nothing moves in 14 days, stop the fiber rather than escalating it, and get the cat examined, because a 14-day trial that failed is information, not a reason to double the dose.

Stop rules

A 14-day trial costs about $6 for a month of psyllium, less than 1 bag of prescription fiber diet, so the cost comparison rarely decides anything. Call the clinic for: no stool in 48 hours, vomiting within 30 minutes of a dose on 2 occasions, straining for more than 10 minutes, blood or mucus that persists past 3 days, or weight loss above 5 percent in 30 days. All of those mean the fiber is either the wrong type, the wrong dose, or irrelevant to the actual problem.

Start this week with 4 steps: weigh 1 teaspoon of your psyllium so you know the grams, buy plain canned pumpkin (not pie filling), begin at half dose for 3 days with 30 ml of water per gram, and log every stool for 14 days with a 1 to 7 score. Then adjust one number at a time - dose, ratio, or water - and give each change 7 days before judging it.

Frequently asked