Senna

Also called Senna alexandrina, Cassia angustifolia, Cassia acutifolia, sennosides.

Best grade B across 5 graded outcomes Botanical Last checked

The short answer

From 19 sources

Senna is a stimulant laxative whose sennosides are activated in the lower gut. In the US it is an over-the-counter drug, not just a supplement. A 90-person placebo-controlled trial and a 2021 systematic review support it for constipation. Labels limit use to 1 week without medical advice; high-dose misuse has been linked to liver injury.

Every graded outcome on this page

5 rows · line = participants
  1. Grade BBowel cleansing before colonoscopy (vs other preparations)Bowel preparationn 3,343
  2. Grade BOverall symptom improvement in chronic idiopathic constipationChronic constipationn 90
  3. Grade CTime to first bowel movement after pelvic surgery (senna with docusate)Constipation after surgeryn 93
  4. Grade DSatisfactory bowel movements in opioid-induced constipation (vs polyethylene glycol)Opioid-induced constipationn 42
  5. Grade DStool retention after anorectal malformation surgery (vs magnesium hydroxide and polyethylene glycol)Constipation after anorectal surgeryn 15
  6. 2 more graded outcomes, in the evidence chapter

Key facts

Regulatory status
US: sold as an over-the-counter laxative drug with a Drug Facts label (sennosides 8.6 mg per tablet); FDA's 2023 final laxative monograph does not list it, and it has stayed in Category III (further testing required) since 1998116
Onset
Generally produces a bowel movement in 6–12 hours, per the label1
Chronic constipation trial
Overall improvement in 69.2% with senna vs 11.7% with placebo over 28 days (90 adults)2
Systematic review
Good evidence (grade A recommendation) for senna and polyethylene glycol as first-line over-the-counter laxatives3
Label limit
Do not use laxatives for longer than 1 week unless directed by a doctor1
Breastfeeding
LactMed: usual doses are acceptable while breastfeeding15

What it is

Senna is a plant stimulant laxative; its sennosides are sold as an over-the-counter drug for occasional constipation.

How it works

Established

Sennosides are dianthrone glycosides that pass through the upper gut intact and are broken down in the lower gut into the active metabolite rhein anthrone, which increases bowel activity. Rhein anthrone itself is scarcely absorbed.1113

Forms, side by side

3 forms named in our sources. The rest show what our data holds, and say plainly where it holds nothing yet.

Senna forms compared

3 forms
Senna forms compared: 3 forms by 3 attributes. Empty cells are labelled No data yet, or Not graded in the evidence row.
3 formsStandardized sennoside tablets (OTC drug)Leaf or pod tea and powdersWith docusate (stool softener)
Absorption in peopleSennosides are activated in the lower gut and the active metabolite is scarcely absorbed.11No head-to-head human data comparing teas with standardized tablets.11No head-to-head human data.4
GI toleranceThe 28-day chronic constipation trial reported no severe treatment-related adverse events.2No tea-specific tolerability data in the cited studies; LiverTox notes liver injury with high doses used longer than recommended.8Tolerability not detailed in the post-surgery trial abstract.4
Studied forConstipation trials and OTC labelling (8.6 mg sennosides per tablet)1.0 g/day of senna in the chronic constipation trialConstipation after pelvic surgery
  1. Standardized sennoside tablets (OTC drug)
    Absorption in people
    Sennosides are activated in the lower gut and the active metabolite is scarcely absorbed.11
    GI tolerance
    The 28-day chronic constipation trial reported no severe treatment-related adverse events.2
    Studied for
    Constipation trials and OTC labelling (8.6 mg sennosides per tablet)
  2. Senna leaf or pod tea and powders
    Absorption in people
    No head-to-head human data comparing teas with standardized tablets.11
    GI tolerance
    No tea-specific tolerability data in the cited studies; LiverTox notes liver injury with high doses used longer than recommended.8
    Studied for
    1.0 g/day of senna in the chronic constipation trial
  3. Senna with docusate (stool softener)
    Absorption in people
    No head-to-head human data.4
    GI tolerance
    Tolerability not detailed in the post-surgery trial abstract.4
    Studied for
    Constipation after pelvic surgery
Every cell holds data from a cited page; citation numbers link to the page that holds them.Scroll the table for every column

What the human research says

Human trials only, one row per outcome. The form line shows what each trial actually tested. Grades follow our evidence-grading policy.

Trial map

5 graded outcomes, largest study first

5 graded outcomes: 2 improved, 3 no effect. The largest, a 2022 meta-analysis of 3,343 people on bowel cleansing before colonoscopy (vs other preparations), found no effect.

2. Time to first bowel movement after pelvic surgery (senna with docusate): improved, 93 people23. Overall symptom improvement in chronic idiopathic constipation: improved, 90 people3
1. Bowel cleansing before colonoscopy (vs other preparations): no effect, 3,343 people14. Satisfactory bowel movements in opioid-induced constipation (vs polyethylene glycol): no effect, 42 people45. Stool retention after anorectal malformation surgery (vs magnesium hydroxide and polyethylene glycol): no effect, 15 people5

1Bowel cleansing before colonoscopy (vs other preparations)

No effect · Grade B · Meta-analysis, 3,343 people, 2022

Patients having colonoscopy (11 trials)

Dose, result and source
Every graded outcome on this page, largest study first
OutcomeFoundPeopleStudyWho was studied
Bowel cleansing before colonoscopy (vs other preparations)No effect3,343Grade B · Meta-analysis, 2022Patients having colonoscopy (11 trials)
Time to first bowel movement after pelvic surgery (senna with docusate)Improved93Grade C · RCT, 2010Adults after pelvic reconstructive surgery
Overall symptom improvement in chronic idiopathic constipationImproved90Grade B · RCT, 2021Adults with chronic idiopathic constipation (mean age 42; 93% women)
Satisfactory bowel movements in opioid-induced constipation (vs polyethylene glycol)No effect42Grade D · Crossover RCT, 2020Outpatients with cancer at risk of or with opioid-induced constipation
Stool retention after anorectal malformation surgery (vs magnesium hydroxide and polyethylene glycol)No effect15Grade D · Crossover RCT, 2025Children with surgically corrected anorectal malformation and constipation
Each circle is one graded outcome on this page, numbered from the largest study down, and placed by how many people it studied (log scale). It shows who was studied and what was found, not advice about your dose.

Every graded row

5 rows

Showing 5 of 5 outcomes. Human trials only.

Grade BBowel cleansing before colonoscopy (vs other preparations)Bowel preparationCleanliness OR 1.02 vs other prepsMeta-analysis · 11 studies
n 3,343 · 2022

No effect Bowel cleanliness was similar to other preparation regimens (OR 1.02; 95% CI 0.63–1.67), with better tolerance (OR 1.66) and compliance (OR 3.05) and more patients free of nausea.

Design
Meta-analysis, 11 studies, n = 3,343, 2022
Population
Patients having colonoscopy (11 trials)
Form
Senna-based bowel preparation regimens
Dose
Varied across trials
Duration
One bowel preparation
Source
Reference 17 · PubMed 35758925 (opens PubMed)
Grade BOverall symptom improvement in chronic idiopathic constipationChronic constipation69% vs 12% respondersRCT
n 90 · 2021

Improved Response rates were 69.2% with senna, 68.3% with magnesium oxide and 11.7% with placebo (P<0.0001); spontaneous bowel movements and constipation quality of life also improved. No severe treatment-related adverse events.

Design
RCT, n = 90, 2021
Population
Adults with chronic idiopathic constipation (mean age 42; 93% women)
Form
Senna
Dose
1.0 g/day of senna
Duration
28 days
Source
Reference 2 · PubMed 32969946 (opens PubMed)
Grade CTime to first bowel movement after pelvic surgery (senna with docusate)Constipation after surgeryImprovedRCT
n 93 · 2010

Improved First bowel movement came sooner than with placebo (3.0 vs 4.05 days; P<.002), and fewer needed magnesium citrate (7.0% vs 43.6%).

Design
RCT, n = 93, 2010
Population
Adults after pelvic reconstructive surgery
Form
Senna (sennosides) with docusate
Dose
8.6 mg sennosides with 50 mg docusate
Duration
After surgery (duration not stated in the abstract)
Source
Reference 4 · PubMed 20207340 (opens PubMed)
Grade DSatisfactory bowel movements in opioid-induced constipation (vs polyethylene glycol)Opioid-induced constipationNo effectCrossover RCT
n 42 · 2020

No effect Days with a satisfactory bowel movement were 1.21 times higher on polyethylene glycol than on sennosides, but the credible interval (0.96–1.55) included no difference; patient preference did not differ.

Design
Crossover RCT, n = 42, 2020
Population
Outpatients with cancer at risk of or with opioid-induced constipation
Form
Sennosides (escalating doses)
Dose
Escalating sennoside doses (amounts not stated in the abstract)
Duration
21 days per period
Source
Reference 5 · PubMed 31321524 (opens PubMed)
Grade DStool retention after anorectal malformation surgery (vs magnesium hydroxide and polyethylene glycol)Constipation after anorectal surgeryNo effectCrossover RCT
n 15 · 2025

No effect Fecal loading on X-ray (Leech score) did not differ: 6.67 with sennosides, 6.80 with magnesium hydroxide and 5.80 with polyethylene glycol (p = 0.841); preference scores did not differ significantly.

Design
Crossover RCT, n = 15, 2025
Population
Children with surgically corrected anorectal malformation and constipation
Form
Sennosides
Dose
Not stated in the abstract
Duration
21 days per period
Source
Reference 19 · PubMed 40856829 (opens PubMed)

What the numbers add up to

Each point is worked out from the data and the sources numbered on this page, with the arithmetic shown under it. It adds no new data and is not medical advice.

Comparable to magnesium oxide

In the same 28-day trial, senna (69.2%) and magnesium oxide (68.3%) had almost identical response rates, both far above placebo (11.7%).2

How we got this: Response rates from the trial abstract

Label maximum vs the trial dose

The adult label maximum of 4 tablets twice daily equals 68.8 mg of sennosides a day; the post-surgery trial abstract gives 8.6 mg per dose but no daily total, so the two cannot be compared directly.14

How we got this: 8 tablets × 8.6 mg = 68.8 mg/day

Studied doses

Doses used in research, shown against the official limits. They describe the studies, not a recommendation for you.

Studied doses in research, not advice. These are amounts used in research, not personal advice. Your clinician or pharmacist can say what fits you.

Doses studied in human trials

Doses studied in human trials ranged from 8.6 mg of sennosides per dose (with docusate; daily total not stated) after surgery to 1.0 g/day of senna for 28 days in chronic constipation; opioid-constipation and children's crossover trials gave sennosides over 21-day periods without stating amounts in the abstract. These are research doses; the OTC label sets its own limits.42519

When trials measured an effect

2 outcomes
How long trials ran before effects were measured
OutcomeMeasured atBasis
Bowel movementGenerally 6–12 hours after a doseDrug Facts label1
Chronic constipation symptom responseMeasured at day 28 (primary endpoint)Placebo-controlled trial of 90 adults2
When each outcome was assessed in the cited trials. It is not a promise of when anyone will notice a change.

Interactions and safety

Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.

What Senna meets

3 cited rows 1 tested together

Medicines 3

Senna3 medicines · 1 supplement

Supplements and foods 1

  • Reference summary
  • Case reports
  • Tested together in a graded trial
Also cited: 1 tested together

  1. Other medicines taken by mouth

    • NIH fact sheetReference summary

      Other medicines taken by mouth: Some senna products should be taken at least 2 hours before or after other oral medicines because they may affect how those medicines work; mineral oil may interact with senna.

      Source 13, MedlinePlus (American Society of Health-System Pharmacists) (2024)

  2. Digoxin and potassium-depleting diuretics

    • Case reportCase reports

      Digoxin and potassium-depleting diuretics, for example digoxin; furosemide, hydrochlorothiazide (diuretic examples inferred): Senna may add to the potassium loss of these diuretics, and its combination with digoxin has been associated with a higher risk of digoxin toxicity, probably through raised digoxin levels and low potassium. Senna's potassium-lowering effect was measured in a dialysis trial: 8 weeks of senna glycoside lowered serum potassium by 0.32 mEq/L versus 0.02 mEq/L with control (73 randomised).

      Source 12, Br J Clin Pharmacol (2024); Source 18, Ther Apher Dial (2022)

  3. Tacrolimus

    • Case reportCase reports

      Tacrolimus: A liver-transplant patient had a 2.8-fold rise in tacrolimus blood level after starting a Cassia angustifolia (senna) product; the authors suggest a P-glycoprotein interaction.

      Source 12, Br J Clin Pharmacol (2024)

  4. Slippery elmSlippery elm page

    • Tested together

      Digestive symptoms and body composition (detox blend with slippery elm). Graded on the Slippery elm page; tested together is not a claim that they work better together.

Rows as our evidence profiles cite them; links stay on this site. Line weight shows what backs a row, not how serious an interaction is. No line means none was found in our sources, not that a combination is safe. Not medical advice: ask your pharmacist.

Interactions

3 agents
Published interactions, grouped by kind
AgentWhat the source saysEvidence
Medicines3
Digoxin and potassium-depleting diureticse.g. digoxin; furosemide, hydrochlorothiazide (diuretic examples inferred)Senna may add to the potassium loss of these diuretics, and its combination with digoxin has been associated with a higher risk of digoxin toxicity, probably through raised digoxin levels and low potassium. Senna's potassium-lowering effect was measured in a dialysis trial: 8 weeks of senna glycoside lowered serum potassium by 0.32 mEq/L versus 0.02 mEq/L with control (73 randomised).1218Case report
TacrolimusA liver-transplant patient had a 2.8-fold rise in tacrolimus blood level after starting a Cassia angustifolia (senna) product; the authors suggest a P-glycoprotein interaction.12Case report
Other medicines taken by mouthSome senna products should be taken at least 2 hours before or after other oral medicines because they may affect how those medicines work; mineral oil may interact with senna.13NIH fact sheet

Check with what you take

Kept on this device only

Add what you take. We list every interaction our evidence profiles cite between Senna and your picks, and between your picks.

Most cited:

Add a supplement or medicine you take to check it against Senna.

Starting from one medicine? The interaction checker rates how serious each pair is, on a curated list of 19 entries for 11 medicines. This cabinet has no severity rating: it lists every interaction row our supplement pages cite.

Not medical advice, and no dosing advice. An empty result means no row we cite names that pair, by name or through a drug class we can link the medicine to, not that a combination is safe. Where our sources name only a group of medicines we cannot match, the cabinet says so. Ask your pharmacist before you combine supplements and medicines.

Who should be careful

6 groups
Use beyond 1 week
The OTC label says not to use laxatives for longer than 1 week unless directed by a doctor.1
Adults 65 and older
MedlinePlus says people 65 or older should talk to a doctor about the risks and benefits first, and that older adults should not usually take senna products over a long period because other medicines for constipation are safer.13
Warning symptoms
The label says to ask a doctor first if you have stomach pain, nausea, vomiting or a change in bowel habits lasting over 2 weeks, and to stop if rectal bleeding occurs or no bowel movement follows.1
Young children
The label says to ask a doctor for children under 2. In poison-centre reports of accidental ingestion by children under 5, 33% developed severe diaper rash and 11% blisters and skin sloughing.19
Pregnancy and breastfeeding
The label advises asking a health professional first. LactMed says usual doses of senna are acceptable while breastfeeding: controlled studies of modern senna products found no effect on breastfed infants, and after 15 mg/day of sennosides median milk transfer was 0.007% of the dose (as rhein). No pregnancy-specific trial data are cited here.11510
High-dose or prolonged misuse
LiverTox reports clinically apparent liver injury with high doses used for longer than recommended.814
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.

Safety first

4 notes

An effective short-term laxative with clear label limits.

Liver injury
LiverTox describes senna as generally safe and well tolerated, but able to cause clinically apparent liver injury when used at high doses for longer than recommended.8
Colorectal cancer question
A prospective case-control study (554 people) found no link between anthranoid laxatives and colorectal adenoma or cancer (OR 1.0); a 2022 meta-analysis found a non-significant trend (OR 1.41, 95% CI 0.94–2.11) and called for better studies.67
Children
Accidental ingestion in young children can cause severe diaper rash and blistering, mostly in children wearing diapers.9
Legal status
US: an over-the-counter drug sold under a Drug Facts label with a laxative purpose. FDA's 2023 final order for OTC laxatives (monograph M007) lists only castor oil and dehydrocholic acid as stimulant laxatives; senna has stayed in Category III (further testing required) since a 1998 proposal.116

How the body handles senna

3 notes

Activated in the colon, little reaches the blood.

Activation
Sennosides are broken down only in the lower gut, releasing rhein anthrone, the active metabolite.11
Absorption
Rhein anthrone is scarcely absorbed, so dianthrone glycosides like sennosides have lower systemic availability than anthraquinone glycosides.11
Breast milk
Rhein in breast milk stayed below 10 ng/mL in 94% of samples after 15 mg/day of sennosides.10

How to read the label

What to check on the Supplement Facts panel.

How to read the label

3 checks
Sennosides per tablet

Standard tablets list 8.6 mg of sennosides as the active ingredient.1

Label dose vs studied dose

Adults and children 12 and over start at 2 tablets once a day (17.2 mg), up to 4 tablets twice a day (68.8 mg); trials used 8.6 mg per dose with docusate or 1.0 g/day of senna.142

Senna with docusate

Combination products add docusate, a stool softener; the post-surgery trial tested this combination, not senna alone.4

Frequently asked questions

Short answers to common questions; the numbers link to the sources below.

Common questions

7 answers
Does senna work for constipation?

Yes, for short-term use. In a 90-person trial, 69% improved on senna vs 12% on placebo, and a 2021 review rated the evidence good.23

Can I use senna every day?

The label says not to use laxatives for longer than 1 week unless a doctor directs it.1

Does long-term senna cause colon cancer?

A case-control study found no link, and a meta-analysis found a non-significant trend that needs better studies.67

How long does senna take to work?

The label says it generally produces a bowel movement in 6–12 hours.1

Is senna a supplement or a drug?

In the US, standardized senna is sold as an over-the-counter drug with a Drug Facts label. FDA's 2023 final laxative monograph does not include it; senna remains in Category III, meaning FDA asked for further testing.116

Is senna safe while breastfeeding?

LactMed says usual doses are acceptable while breastfeeding: controlled studies of modern senna products found no effect on breastfed infants, and very little reached milk in a 20-woman study. The label still says to ask a health professional first.15101

Is senna used to prepare for a colonoscopy?

Yes, as a medical use. In an 11-trial meta-analysis (3,343 patients), senna-based preparations cleaned the bowel about as well as other regimens, with better tolerance and compliance.17

Sources

19 sources: trial abstracts, NIH fact sheets and reference databases. Numbers in the text link here.

Sources cited on this page

19 sources
  1. 1SENOKOT (standardized senna concentrate) tablet: Drug Facts labelLabel DailyMed, U.S. National Library of Medicine, 2025 · dailymed.nlm.nih.gov
  2. 2Senna Versus Magnesium Oxide for the Treatment of Chronic Constipation: A Randomized, Placebo-Controlled Trial.RCT Am J Gastroenterol, 2021 · PMID 32969946
  3. 3Efficacy and Safety of Over-the-Counter Therapies for Chronic Constipation: An Updated Systematic Review.Systematic review Am J Gastroenterol, 2021 · PMID 33767108
  4. 4The use of senna with docusate for postoperative constipation after pelvic reconstructive surgery: a randomized, double-blind, placebo-controlled trial.RCT Am J Obstet Gynecol, 2010 · PMID 20207340
  5. 5PEG vs. sennosides for opioid-induced constipation in cancer care.Crossover RCT Support Care Cancer, 2020 · PMID 31321524
  6. 6Anthranoid laxative use is not a risk factor for colorectal neoplasia: results of a prospective case control study.Observational Gut, 2000 · PMID 10764708
  7. 7Anthraquinone laxatives use and colorectal cancer: A systematic review and meta-analysis of observational studies.Meta-analysis Phytother Res, 2022 · PMID 35040201
  8. 8Senna.Database LiverTox: Clinical and Research Information on Drug-Induced Liver Injury, 2012 · PMID 31643257
  9. 9Skin breakdown and blisters from senna-containing laxatives in young children.Observational Ann Pharmacother, 2003 · PMID 12708936
  10. 10Relevance of rhein excretion into breast milk.PK study Pharmacology, 1988 · PMID 3368521
  11. 11Metabolism and pharmacokinetics of anthranoids.Review Pharmacology, 1993 · PMID 8234447
  12. 12Cassia angustifolia and tacrolimus interaction in a liver transplant patient, a case report.Observational Br J Clin Pharmacol, 2024 · PMID 38657592
  13. 13SennaFact sheet MedlinePlus (American Society of Health-System Pharmacists), 2024 · medlineplus.gov
  14. 14Senna-induced hepatitis in a poor metabolizer.Observational Ann Intern Med, 2004 · PMID 15492352
  15. 15Senna. Drugs and Lactation Database (LactMed)Database National Institute of Child Health and Human Development, 2024 · ncbi.nlm.nih.gov
  16. 16Over-the-Counter Monograph M007: Laxative Drug Products for Over-the-Counter Human Use (Final Administrative Order OTC000032)Guideline U.S. Food and Drug Administration, 2023 · accessdata.fda.gov
  17. 17The Efficacy of Senna Bowel Preparation for Colonoscopy: A Systematic Review and Meta-analysis.Meta-analysis Gastroenterol Nurs, 2022 · PMID 35758925
  18. 18Effect of senna glycoside on serum potassium levels among patients on maintenance hemodialysis: A randomized controlled trial.RCT Ther Apher Dial, 2022 · PMID 38318690
  19. 19Sennosides vs magnesium hydroxide vs polyethylene glycol as a treatment for constipation in anorectal malformation: a randomized crossover trial.Crossover RCT Pediatr Surg Int, 2025 · PMID 40856829

What changed

Every dated change to this page: what changed, who made it and why.

Change log

4 entries
Dated changes to this page
DateChangeWho and why
key facts, evidence, studied doses, interactions, who should be careful, safety, FAQAdded a colonoscopy bowel-preparation meta-analysis (PMID 35758925, 11 trials, marked as a medical use) and a children's crossover trial after anorectal malformation surgery (PMID 40856829, grade D). Pregnancy and breastfeeding notes now cite the NIH LactMed senna record (revised 2024; PMID 30000408). Regulatory status now cites FDA's 2023 final OTC laxative order (monograph M007), which leaves senna in Category III. The diuretic interaction adds a dialysis trial on potassium (PMID 38318690). Added a colonoscopy FAQ. A 2024 meta-analysis on opioid-induced constipation in cancer (PMID 38452708) only restates the existing polyethylene glycol vs sennosides trial, so no row was added.Writer: Kymata Health EditorialTrigger: A–Z page audit
allIndependent adversarial review: post-surgery 8.6 mg sennoside dose labelled per dose (the abstract gives no daily total) and the label-maximum insight reworded so it no longer compares a daily maximum with a single dose; added the MedlinePlus caution for adults 65 and older and against long-term use in older adults.Writer: Kymata Health EditorialTrigger: review
allAdversarial review pass: every evidence row, key fact, interaction, safety note and FAQ re-read against its PubMed abstract or source page, and every number machine-checked against the cited source text. Retraction, expression-of-concern and withdrawn checks on all PMIDs: none flagged. Fixes: activation described as in the lower gut (the abstract does not name bacteria); an unsourced tea-standardisation claim and an unstated trial country removed.Writer: Kymata Health EditorialTrigger: review
allInitial editorial evidence review (first draft). Every PMID checked against NCBI E-utilities esummary (titles and years taken from the record) and the abstract read for each cited row. Studied doses are reported as research doses, not dosing advice.Writer: Kymata Health EditorialTrigger: new page

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