FortiFlora is a veterinary probiotic supplement made by Purina Pro Plan that contains live beneficial bacteria designed to support digestive health in cats. It comes as a flavored powder in single-serve sachets, each delivering 100 million colony-forming units of a specific probiotic strain. Vets commonly recommend it for diarrhea, antibiotic-related gut disruption, and stress-induced digestive problems.
What’s Inside Each Sachet
The active ingredient is a probiotic bacterium called Enterococcus lactis SF68, dosed at 100 million live organisms per one-gram packet. The supplement also contains 5 mg of taurine, an amino acid that’s essential for cats (they can’t produce enough on their own and need it for heart and eye health).
The inactive ingredients are liver flavor and yeast. The liver flavor, which Purina previously listed as “animal digest,” comes from hydrolyzed pork liver and poultry. This is what gives the powder its strong meaty smell and makes most cats eat it willingly, even when they’re feeling off. You sprinkle it on top of wet or dry food once a day.
How It Works in the Gut
The SF68 strain works through several overlapping mechanisms. It directly competes with harmful bacteria for space and resources along the intestinal lining, making it harder for disease-causing microbes to take hold. It also strengthens the gut’s immune barrier by boosting production of an antibody called IgA, which acts as a first line of defense on mucosal surfaces like the intestinal wall.
One of the more interesting findings involves microbial diversity. Cats given a placebo during stressful situations showed a drop in the variety of bacteria in their gut, while cats supplemented with SF68 maintained their normal diversity. This matters because a diverse gut microbiome is more resilient and better at recovering from disruptions like illness, dietary changes, or environmental stress.
What Vets Use It For
The most common reason vets recommend FortiFlora is acute diarrhea. In clinical research, only 7.7% of cats receiving the probiotic experienced diarrhea lasting two or more days, compared to 20.7% in the placebo group. That’s a meaningful difference for a supplement with very few downsides.
Beyond straightforward diarrhea, FortiFlora is frequently recommended in these situations:
- Antibiotic courses. Antibiotics kill beneficial gut bacteria alongside the harmful ones, often causing loose stools. FortiFlora helps preserve microbial balance during and after treatment.
- Stress-related digestive upset. Boarding, travel, moving, or a new pet in the home can throw off a cat’s digestion. The probiotic helps maintain gut stability during these transitions.
- Immune support. Cats supplemented with SF68 over longer periods showed improved immune responses. In one study, cats with chronic feline herpesvirus 1 infections showed fewer symptoms over time while taking the probiotic, suggesting a broader immune-modulating effect beyond the gut.
How to Give It
The standard dose is one sachet per day, sprinkled on top of your cat’s main meal. Purina’s guidelines are straightforward: for digestive issues, continue daily until at least one week after stools return to normal. For immune support, one sachet daily on an ongoing basis.
If your cat is on antibiotics, timing matters. Give FortiFlora at least two hours apart from the antibiotic dose. Otherwise, the antibiotic can kill off the probiotic bacteria before they reach the gut. Continue the supplement throughout the entire antibiotic course and for one week after the last dose. This gap gives the gut flora time to restabilize.
Safety and Side Effects
Probiotics in general have a strong safety profile, and FortiFlora is no exception. The most commonly reported side effects are mild gas or temporary stomach discomfort, particularly in the first few days. These tend to resolve on their own as the gut adjusts.
There are a few situations where caution is warranted. Cats that are severely immunocompromised should not take probiotics, because even beneficial bacteria could pose a risk when the immune system can’t regulate them properly. Allergic reactions are rare but possible, typically triggered by the inactive ingredients (the liver flavoring or yeast) rather than the probiotic strain itself. Antifungal medications can also reduce the supplement’s effectiveness if given at the same time.
Why Cats Actually Eat It
One of FortiFlora’s practical advantages is that most cats find it genuinely appealing. The hydrolyzed liver flavoring gives it a strong savory taste, and many cat owners report that even picky eaters will clean their bowl when the powder is sprinkled on top. Some vets recommend it specifically for this reason when trying to get a reluctant cat to eat a new prescription diet or medication mixed into food. The powder dissolves into wet food easily and sticks to the surface of dry kibble without much fuss.