What it's used for
This medication is used to prevent and treat portal-systemic encephalopathy, including stages of hepatic pre-coma and coma, by helping lower blood ammonia levels.
Source: U.S. FDA-approved prescribing information (openFDA).
Typical dosing
The usual adult oral dose is 2 to 3 tablespoonfuls three or four times daily, adjusted to produce 2 to 3 soft stools per day.
Dosing shown here is the general FDA-labeled range. Your prescribing clinician determines the exact dose, form, and schedule for you — this is not a substitute for medical advice.
Boxed warning / key safety info
This medication can lead to a buildup of gas that poses an explosion risk during certain surgical procedures involving electrical instruments.
Common side effects
Common side effects include gas, bloating, belching, and abdominal discomfort or cramping.
Covered strengths on the Tab $0 list
Covered at $0 with an active Tab membership when filled at a participating pharmacy nationwide or through mail order. A licensed clinician must prescribe the medication.
Related medications
Other everything else medications covered at $0 with an active Tab membership.
Lactulose cost without insurance
Cash prices for Lactulose without insurance vary widely by pharmacy, strength and quantity — the same prescription can cost very different amounts at two pharmacies in the same town. That is the problem a membership solves.
Lactulose is on Tab's covered $0 generic list. With an active Tab membership, every covered strength is $0 — not a percentage off, not a coupon that changes month to month — at participating pharmacies nationwide or through mail order. You do not need insurance, and Tab works whether or not you have a health plan.
Tab is a membership, not insurance. Covered medications require a prescription from a licensed clinician.
Lactulose dosage and administration
Oral Adult: The usual adult, oral dosage is 2 to 3 tablespoonfuls (30 to 45 ml, containing 20 g to 30 g of lactulose) three or four times daily. The dosage may be adjusted every day or two to produce 2 or 3 soft stools daily. Hourly doses of 30 to 45 ml of Lactulose may be used to induce the rapid laxation indicated in the initial phase of the therapy of portal-systemic encephalopathy. When the laxative effect has been achieved, the dose of lactulose may then be reduced to the recommended daily dose. Improvement in the patient's condition may occur within 24 hours but may not begin before 48 hours or even later. Continuous long-term therapy is indicated to lessen the severity and prevent the recurrence of portal-systemic encephalopathy. The dose of lactulose for this purpose is the same as the recommended daily dose.
Excerpt from the FDA-approved prescribing information (openFDA), retrieved 2026-09-15. Your prescribing clinician decides the exact dose, form and schedule for you — this is not medical advice.
Lactulose side effects
Precise frequency data are not available. Lactulose may produce gaseous distention with flatulence or belching and abdominal discomfort such as cramping in about 20% of patients. Excessive dosage can lead to diarrhea with potential complications such as loss of fluids, hypokalemia, and hypernatremia. Nausea and vomiting have been reported. To report SUSPECTED ADVERSE EVENTS, contact the FDA at 1-800-FDA-1088 or http://www.fda.gov/ for voluntary reporting of adverse reactions.
Excerpt from the FDA-approved prescribing information (openFDA), retrieved 2026-09-15. This is not a complete list. Report side effects to your clinician, and seek care for anything severe or unexpected.
Lactulose drug interactions
There have been conflicting reports about the concomitant use of neomycin and lactulose solution. Theoretically, the elimination of certain colonic bacteria by neomycin and possibly other anti-infective agents may interfere with the desired degradation of lactulose and thus prevent the acidification of colonic contents. Thus the status of the lactulose-treated patient should be closely monitored in the event of concomitant oral anti-infective therapy. Results of preliminary studies in humans and rats suggest that nonabsorbable antacids given concurrently with lactulose may inhibit the desired lactulose-induced drop in colonic pH. Therefore, a possible lack of desired effect of treatment should be taken into consideration before such drugs are given concomitantly with lactulose.
Excerpt from the FDA-approved prescribing information (openFDA), retrieved 2026-09-15. Tell your clinician and pharmacist about every medication, supplement and over-the-counter product you take.
Who should not take lactulose
Since lactulose solution contains galactose (less than 1.6 g/15 mL), it is contraindicated in patients who require a low galactose diet.
Excerpt from the FDA-approved prescribing information (openFDA), retrieved 2026-09-15. Whether this medication is appropriate for you is a clinical decision made by your prescribing clinician.
Common questions
Is lactulose covered at $0 with Tab?
Yes. Lactulose is on Tab's covered $0 generic list — every covered strength is $0 with an active membership, at participating pharmacies nationwide or by mail order.
Do I need insurance to get lactulose through Tab?
No. Tab is a membership, not insurance. Covered medications are $0 with an active membership whether or not you have a health plan.
How do I get a lactulose prescription with Tab?
Book a video visit with a licensed Tab clinician (unlimited visits are included with membership). If it's clinically appropriate, they send the prescription to your chosen participating pharmacy or by mail order.
How much does lactulose cost without insurance?
Without insurance, retail cash prices for lactulose vary by pharmacy, strength and quantity. Lactulose is on Tab's covered $0 generic list, so every covered strength is $0 with an active Tab membership at participating pharmacies nationwide or by mail order.
What is the cheapest way to get lactulose?
For medications on Tab's covered list, a Tab membership is the cheapest route: covered strengths of lactulose are $0 with an active membership, and unlimited video visits with a licensed clinician are included, so the visit that produces the prescription is covered too.
What is the usual dose of lactulose?
Oral Adult: The usual adult, oral dosage is 2 to 3 tablespoonfuls (30 to 45 ml, containing 20 g to 30 g of lactulose) three or four times daily. The dosage may be adjusted every day or two to produce 2 or 3 soft stools daily. Hourly doses of 30 to 45 ml of Lactulose may be used to induce the rapid laxation indicated in the initial phase of the therapy of portal-systemic encephalopathy. (FDA-approved label, retrieved 2026-09-15. Your clinician sets your dose.)
What are the side effects of lactulose?
Precise frequency data are not available. Lactulose may produce gaseous distention with flatulence or belching and abdominal discomfort such as cramping in about 20% of patients. Excessive dosage can lead to diarrhea with potential complications such as loss of fluids, hypokalemia, and hypernatremia. Nausea and vomiting have been reported. (FDA-approved label, retrieved 2026-09-15.)
What interacts with lactulose?
There have been conflicting reports about the concomitant use of neomycin and lactulose solution. Theoretically, the elimination of certain colonic bacteria by neomycin and possibly other anti-infective agents may interfere with the desired degradation of lactulose and thus prevent the acidification of colonic contents. (FDA-approved label, retrieved 2026-09-15. Tell your clinician about every medication and supplement you take.)
Lactulose is $0 on the covered list
Members pay $0 for covered generics at participating pharmacies nationwide or by mail order — plus unlimited virtual primary care, urgent care and dermatology visits. No insurance needed.
Solo $49/mo · Family $119/mo for up to 4 people · Family+ $149/mo for up to 8
Start your membership → Compare plansTab is a membership and prescription-discount program, not insurance. A licensed clinician must prescribe any medication. Cancel anytime — no renewal.