How long does it take for bismuth to get out of your system?

October 9, 2025 •

4 min read

While the darkening of the stool and tongue, a common side effect of bismuth subsalicylate (e.g., Pepto-Bismol), typically resolves within a few days after stopping the medication, a small portion of the absorbed bismuth can take weeks to months to get out of your system completely. This surprising difference is due to the dual pathways the body uses to eliminate bismuth, with the majority passing quickly and a small fraction undergoing a slow, systemic clearance.

Quick Summary

The majority of bismuth is unabsorbed and eliminated quickly in feces, causing temporary black stools. A small amount is absorbed systemically and cleared slowly by the kidneys, with half-lives ranging from weeks to months, leading to prolonged retention in some tissues.

Key Points

Two-stage elimination: Most bismuth is unabsorbed and cleared within days, while a small, absorbed portion takes weeks to months to fully eliminate.
Quick fecal clearance: The rapid elimination of unabsorbed bismuth causes the temporary and harmless blackening of the tongue and stool, which clears in a few days.
Slow renal clearance: Absorbed bismuth is slowly eliminated via the kidneys, with a half-life extending over weeks, explaining its prolonged presence in the body.
Prolonged retention in tissues: The small amount of absorbed bismuth can distribute and accumulate in tissues like the kidneys, liver, and bone, further contributing to its slow systemic clearance.
Risk of accumulation with chronic use: Long-term or high-dose use increases the amount of absorbed bismuth, potentially leading to accumulation and, in rare cases, toxicity.
Kidney function is a factor: The speed of systemic bismuth elimination is dependent on kidney health; impaired function can significantly prolong clearance.

Understanding Bismuth Elimination

When you take an oral medication containing bismuth subsalicylate, such as Pepto-Bismol, its elimination is not a single, straightforward process. Instead, the body handles the compound in two very different ways based on how it's absorbed. The vast majority of the bismuth is not absorbed into the bloodstream at all. The small, residual portion that is absorbed, however, follows a much longer and more complex elimination route. This dual pathway explains why visible side effects disappear quickly, while traces of the element can linger for an extended period.

The Quick Exit: Fecal Elimination of Unabsorbed Bismuth

Most of the bismuth subsalicylate ingested travels through the gastrointestinal (GI) tract and remains unabsorbed. During this process, colonic bacteria react with the bismuth to form bismuth sulfide, a black-colored compound. It is the formation of this sulfide that causes the harmless and temporary black stools and tongue discoloration commonly associated with the medication. This unabsorbed portion is eliminated in the feces within a few days of stopping the medication. The speed of this process depends on an individual's bowel regularity, but for most people, the cosmetic side effects are short-lived.

The Slow Release: Systemic Elimination of Absorbed Bismuth

While most bismuth is unabsorbed, a small fraction (less than 0.005% from bismuth subsalicylate) is absorbed systemically into the bloodstream. This small amount is then distributed to various body tissues, with a particular affinity for organs like the kidneys, liver, and spleen. The body struggles to excrete this absorbed bismuth, leading to a multi-phase elimination process with a significantly longer half-life than the unabsorbed portion.

Research indicates that absorbed bismuth is cleared from the body in phases. Studies have shown an intermediate half-life of 5 to 11 days, followed by a much longer terminal half-life of 21 to 72 days. Some long-term studies have even suggested detectable levels for months after the last dose, with a washout period of approximately two months often cited. The slow excretion primarily occurs via the kidneys through urinary output. This prolonged elimination is why, even long after visible side effects have passed, trace amounts of the element can still be present in the body.

Factors Influencing Bismuth Clearance

Several factors can influence the rate at which bismuth is eliminated from the system, potentially prolonging its presence in the body. These include:

Dosage and Duration of Use: The amount of bismuth absorbed is directly related to the dose and length of treatment. Chronic use or high dosages lead to greater systemic absorption and can result in higher blood concentrations, requiring a longer period for complete clearance.
Kidney Function: Because the kidneys are the primary route for eliminating absorbed bismuth, impaired renal function can significantly delay clearance. Individuals with kidney disease are at a higher risk of bismuth accumulation and potential toxicity.
Hydration Status: Proper hydration helps support kidney function and the urinary excretion of drugs and toxins. Dehydration may slow the elimination process.
Individual Variation: A person's metabolic rate and overall health can play a role. As with most medications, pharmacokinetics can vary between individuals.

Comparison of Elimination Timelines


Aspect	Unabsorbed Bismuth	Absorbed Bismuth
Pathway	Primarily fecal excretion	Primarily urinary excretion (via kidneys)
Speed	Relatively fast	Very slow, multi-phase
Visible Effect	Black stools, black tongue	None (requires lab tests to detect)
Clearance Timeline	Days (typically 2-3 days after stopping)	Weeks to months (intermediate half-life of 5-11 days, terminal half-life of 21-72 days)
Cause of Effect	Reaction with sulfur in the GI tract	Systemic absorption and tissue binding

Chronic vs. Acute Bismuth Exposure

Most people take bismuth subsalicylate for a few days to relieve a temporary upset stomach. In these cases, systemic absorption is minimal and accumulation is not a concern. The time needed to clear the absorbed portion is relatively short compared to chronic, high-dose users. However, in cases of chronic, long-term use (such as for certain medical conditions), the concentration of absorbed bismuth can build up in the body over time. This accumulation necessitates a longer washout period and carries a higher risk of adverse effects, including neurotoxicity in rare instances. A study on subjects receiving a repeated-dose regimen found that bismuth concentration in the blood remained detectable at 60 days after drug withdrawal, indicating a washout period of approximately two months for the absorbed component.

Conclusion

In summary, the question of how long it takes for bismuth to leave your system has two answers, depending on which portion of the medication is being considered. The majority of the dose, which is not absorbed, is eliminated through the feces within a few days, along with the tell-tale blackening of the stool and tongue. However, the small amount that is absorbed systemically is eliminated much more slowly, with a multi-phase process that can see traces of the element persist for weeks or even months. Factors like kidney function, dosage, and duration of use can further influence this timeline. It is this slow elimination of the absorbed component that warrants caution in chronic, long-term use and underscores the importance of not exceeding recommended dosage guidelines.

Authority Link

For detailed pharmacological information on bismuth subsalicylate, the U.S. National Institutes of Health provides comprehensive data in its StatPearls reports: Bismuth Subsalicylate - StatPearls - NCBI Bookshelf.

A Note on Chronic Use and Toxicity

High-dose, chronic bismuth use has been linked to rare but serious side effects, such as neurotoxicity and encephalopathy. The slow elimination of absorbed bismuth from the kidneys and other tissues contributes to this risk. For this reason, it is crucial to follow dosage instructions precisely and consult a healthcare provider for any questions regarding long-term use.

Frequently Asked Questions

Your stools turn black because the bismuth in the medication reacts with trace amounts of sulfur present in your gastrointestinal tract. This forms bismuth sulfide, a dark-colored substance that is harmless and temporary.

The blackening of your tongue and stools is a temporary and harmless side effect that typically goes away within a few days after you stop taking the medication.

Yes, a very small amount of bismuth from oral medications like bismuth subsalicylate (less than 0.005%) is absorbed into the bloodstream. This absorbed portion has a much longer elimination time than the unabsorbed part.

Yes, chronic or high-dose use of bismuth can lead to the accumulation of absorbed bismuth in body tissues, especially the kidneys. This increases the amount of time it takes to fully clear from the system.

The elimination of absorbed bismuth follows a multi-phase process. It has an intermediate half-life of 5 to 11 days and a longer terminal half-life of 21 to 72 days.

In cases of long-term, high-dose exposure, the accumulation of bismuth can become toxic, potentially causing rare side effects like neurotoxicity. For typical, short-term use, the absorbed amounts are very low and considered safe.

For the typical, unabsorbed bismuth causing black stools, stopping the medication is sufficient, and the effect will resolve within a few days. The elimination of absorbed bismuth is a slow process primarily handled by the kidneys and cannot be significantly accelerated through home remedies. Ensuring adequate hydration supports normal kidney function.