TUDCA Side Effects: What Clinical Trials Recorded

In the controlled trials that give numbers for both groups, side effects were about as common on TUDCA as on placebo or on ursodiol (UDCA), a long-established prescription bile acid, and the ones reported most often were digestive, such as looser stools, nausea, indigestion and stomach pain. Few serious events were recorded on TUDCA, and the medicine labels list the situations in which it shouldn't be taken.

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Before trying any supplement, most people want to know two things: what side effects it can cause, and whether it is safe to take for a long time. For TUDCA, the answers online range from claims of no side effects to long lists of problems with no source behind them.

This guide sticks to what the clinical trials actually recorded. It explains how often side effects happened, how that compared with placebo, which ones were most common, what the trials didn't record, and who should avoid TUDCA altogether. Our TUDCA safety review sets out every study in full.

What Are the Side Effects of TUDCA?

Most of the side effects people reported on TUDCA were digestive, mainly looser stools or diarrhea, nausea, indigestion and stomach pain [1, 2, 3]. Where a trial counted side effects in both groups, the TUDCA group had about as many as the group on placebo or on UDCA [1, 2, 3].

A trial logs every health problem that comes up during the study, whether or not the treatment caused it. That is why the comparison group matters: a side effect that is just as common on placebo is less likely to be caused by TUDCA itself.

What Did the Clinical Trials Record?

Here is what the controlled trials found, in plain terms. Each was in people with a specific condition.

1. A year-long trial against placebo

In people with ALS taking 2 g a day for 54 weeks, side effects judged related to treatment occurred in 2 of 15 people on TUDCA and 3 of 14 on placebo, and mild diarrhea in 2 people in each group [3]. Blood counts and liver tests didn't change in either group.

2. A 16-week trial against placebo

In people with multiple sclerosis taking 2 g a day, any side effect was recorded in 38% on TUDCA and 33% on placebo [2]. Ten digestive side effects were recorded among 26 people on TUDCA and four among 21 on placebo, a difference that wasn't statistically significant; on TUDCA they included diarrhea in three people, nausea or vomiting in two, indigestion or reflux in two and abdominal pain in two.

3. A 24-week trial against the prescription bile acid

In 199 people with primary biliary cholangitis, a chronic bile duct disease, health problems were recorded about as often on TUDCA as on UDCA, 44% and 40% [1]. Side effects judged related to the medicine occurred in 4 of 129 people on TUDCA (diarrhea, itching, rash and period pain) and 3 of 70 on UDCA.

Not every comparison with UDCA was this even. Two Italian trials from 1993, with 25 and 31 people who finished, found UDCA better tolerated, without giving counts [4, 5].

4. The one study after gallbladder removal

In 203 adults with indigestion after gallbladder removal, side effects were reported in 2 of 101 people taking 500 mg a day and 3 of 102 who took nothing [6]. The study's published summary doesn't describe them.

Can TUDCA Cause Diarrhea?

Yes, in some people. Earlier ALS trials reported soft stools or short-lived diarrhea after the first doses [7]. In the year-long placebo-controlled trial, mild diarrhea was just as common on placebo [3]; in the 16-week multiple sclerosis trial, diarrhea was recorded in 3 of 26 people on TUDCA and none of 21 on placebo [2]; and in an Italian ALS registry, diarrhea was the side effect recorded most often, in 12 of 86 people [8]. The Italian Tudcabil and Turkish Taurolite labels say to lower the dose if diarrhea occurs and to stop if it continues [9, 10].

A few people notice looser stools when they first start; take it with a meal, as directed. Our guide to TUDCA and bowel changes covers loose stools, constipation and what stool color can tell you.

What Side Effects Weren't Recorded?

Some symptoms people ask about don't appear among the side effects recorded in the TUDCA studies we could read. In those studies, constipation, headache, insomnia and bloating weren't named as side effects on TUDCA, and the one case of constipation recorded in a TUDCA trial was on placebo [2]. Itching and rash were each recorded in a small number of people, for example 2 of 129 and 1 of 129 in the liver trial [1].

Not being recorded isn't the same as never happening, because trials don't always list minor complaints. In online forums, some people describe stomach pain, gas or constipation after starting TUDCA, while others notice no change. If a new symptom appears, it is worth noting when it started and stopping to see whether it goes away.

Is TUDCA Safe Long Term?

In the one placebo-controlled trial that ran for about a year, side effects were no more common on TUDCA than on placebo [3], but we found no study following healthy adults for several years. In the Italian registry, 44 of 86 people took TUDCA for 12 months or more, and across all 86, 7 stopped because of side effects and 13 lowered their dose [8]. In a 12-month trial of 20 people with type 1 diabetes, whose results are posted only on a trial registry, no side effects or abnormal liver tests were reported in either group [11].

Most studies ran for six months or less, and every study that ran for a year or longer was in people with a specific condition, such as ALS or type 1 diabetes. Our guide to how long to take TUDCA covers long-term use in more detail.

Were There Any Serious Side Effects?

In the controlled trials that report serious events, one person on TUDCA had a serious event other than death from their illness. In the multiple sclerosis trial, one person on TUDCA was hospitalized with inflammation of the bile ducts and recovered; the trial's safety board judged it unlikely to be related, and scans showed long-standing bile duct abnormalities [2]. No serious events were recorded in the 199-person liver trial [1].

The investigators didn't attribute any trial deaths to TUDCA. In the year-long ALS trial, one person on TUDCA and three on placebo died of respiratory failure from the disease [3]. In the Italian registry, two side effects led to a hospital stay and cleared up once TUDCA was stopped [8].

Can TUDCA Cause Liver Damage?

We found no published report of liver injury blamed on TUDCA. In the one case report of liver injury in someone taking it, doctors attributed the injury to a different drug taken at the same time [12]. In trials of people with liver conditions, liver enzymes generally fell on TUDCA rather than rose [13, 14, 1]. If you notice signs of liver injury after starting any new medicine or supplement, such as abdominal pain, dark urine or yellowing of the skin or eyes, contact your doctor [15]. Our guide to TUDCA for liver health covers the liver data, including FDA's reports.

Who Should Not Take TUDCA?

The medicine labels rule TUDCA out in pregnancy, with an active stomach or duodenal ulcer and with some gallbladder and bile duct problems, and the Italian label adds breastfeeding [9, 10]. They also list medicines to space or avoid. Our guide to who should not take TUDCA goes through each caution.

Where Does TUDCA Fit After Gallbladder Removal?

After gallbladder removal, bile flows directly from the liver into the small intestine instead of being stored for meals [16]. Dr.Primal's TUDCA is made for life after gallbladder removal and taken with meals, when your body calls on bile the most, to support healthy bile flow and fat digestion.

In Summary: TUDCA Side Effects

In the controlled trials that give numbers for both groups, side effects were about as common on TUDCA as on placebo or on UDCA, and the ones reported most often were digestive. Few serious events were recorded on TUDCA, though most studies were short and none was in healthy adults over several years. The labels set out who shouldn't take it.

If you are working out what is behind your own symptoms after meals, our digestion quiz is a quick way to put your symptoms and habits in order.

This article is for general education and is not a substitute for advice from your doctor. TUDCA is sold as a dietary supplement. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.