Diarrhea is not a common side effect of diazepam during normal use, but it can happen. In clinical trials of a rectal gel formulation, about 4% of patients reported diarrhea compared to less than 1% on placebo. The oral tablet’s FDA label doesn’t list diarrhea among its recognized side effects at all, though it does list constipation and nausea as occasional gastrointestinal reactions. So while diarrhea is possible, it’s far from typical.
What the Prescribing Labels Actually Say
The FDA-approved label for Valium (the brand-name oral tablet) lists constipation and nausea as the gastrointestinal side effects to watch for. Diarrhea doesn’t appear on that list. The most commonly reported effects overall are drowsiness, fatigue, and coordination problems.
The picture changes slightly with the rectal gel formulation, where diarrhea showed up in 4% of trial participants versus less than 1% on placebo. This likely reflects the route of delivery: medication applied directly to the rectum can irritate the lining and trigger loose stools. If you’re using a rectal form and experiencing diarrhea, the formulation itself may be the cause rather than the drug.
Withdrawal Is a More Common Trigger
Here’s what many people searching this question may actually be experiencing: diarrhea is a recognized symptom of benzodiazepine withdrawal. The FDA label explicitly lists gastrointestinal reactions, including nausea, vomiting, diarrhea, weight loss, and decreased appetite, among the acute withdrawal signs associated with benzodiazepines.
This matters because withdrawal symptoms can appear even without fully stopping the medication. Reducing your dose, missing doses, or taking the drug inconsistently can all produce mild withdrawal effects. If your diarrhea lines up with a change in your dosing pattern rather than with starting the medication, withdrawal is the more likely explanation.
Lactose in the Tablets
Every strength of Valium tablets contains anhydrous lactose as an inactive ingredient. If you’re lactose intolerant, this filler could be triggering digestive symptoms that feel like a side effect of the drug itself. The amount of lactose in a single tablet is small, but people with significant lactose sensitivity can react to even trace amounts, especially when taking the medication daily.
Generic diazepam tablets may use different inactive ingredients depending on the manufacturer. If you suspect lactose is the issue, checking the ingredient list on your specific generic or asking your pharmacist about a lactose-free formulation is a practical first step.
Why Diazepam Typically Slows the Gut
Benzodiazepines as a class tend to slow digestion rather than speed it up. They work by enhancing the activity of a calming brain chemical, and this sedating effect extends to the smooth muscle in the digestive tract. That’s why constipation appears on the side effect list and diarrhea generally doesn’t. If anything, most people notice their bowels become slightly more sluggish on diazepam, not less.
This also means that if you do develop diarrhea shortly after starting diazepam, it’s worth considering other explanations: a change in diet, stress, another medication you started around the same time, or the lactose issue mentioned above. The drug itself is more likely to have the opposite effect on gut motility.
Sorting Out the Cause
Timing is the most useful clue. Diarrhea that starts within the first few days of taking diazepam could point to a sensitivity to the drug or its inactive ingredients. Diarrhea that appears after you reduce your dose or stop taking it suggests withdrawal. And diarrhea that comes and goes without a clear pattern may not be related to the medication at all.
If you’re taking the rectal gel formulation, mild diarrhea is a known possibility and affects roughly 1 in 25 users. For oral tablets, persistent diarrhea is uncommon enough that other causes deserve investigation before attributing it to diazepam. Keeping a simple log of when symptoms appear relative to your doses can help you and your provider figure out what’s going on.