Constulose (lactulose) prescription available online 

If you are suffering from constipation, Constulose (lactulose) can help. Get a new prescription or refill of Constulose today from a board-certified doctor online.*

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Helps relieve constipation and discomfort

Same-day appointments to evaluate constipation symptoms

Save up to 66.33% on Constulose with RX discount card*

*Prescriptions are provided at the doctor’s discretion. Learn more about our controlled substances policy and how you can save up to 80% with our prescription discount card.

About Constulose (lactulose)

Constulose is considered a laxative, which helps increase the number of normal bowel movements per day and the number of days you have a bowel movement.

Constulose is used to treat chronic constipation. It can also help treat or prevent certain conditions of the brain caused by liver disease. Constulose is available only by prescription. It is available in a generic formulation as well as under different brand names, including lactulose.

Constulose may be prescribed as an oral solution. It’s always important to follow the specific instructions on your prescription, as they can vary based on the formulation and dosage prescribed.

If you're prescribed Constulose, be sure to complete the full course of the laxative unless your doctor specifically tells you to stop. If you don’t complete your prescription, the laxative may not fully treat your chronic constipation.

Constulose uses

There are several FDA-approved uses for Constulose, but it may also be used off-label to treat other conditions. Your online medical professional may prescribe it for any of the following common reasons. It’s also possible that your healthcare provider may prescribe it for other reasons not listed here. If you have questions about why a medication is prescribed, ask your online doctor or pharmacist.

  • Chronic constipation

    Constulose is FDA-approved to treat chronic constipation. Lactulose solution helps increase the number of bowel movements per day and the number of days that you have a normal bowel movement.

  • Hepatic encephalopathy

    Constulose is FDA-approved to treat hepatic encephalopathy, a condition where the liver does not remove toxins from the body. Lactulose may help decrease toxins in the blood, which helps reduce symptoms.

Constulose side effects

  • The side effects associated with taking Constulose are typically mild. Most Constulose side effects are associated with gastrointestinal discomfort. Constulose has some common side effects. They may include:

    • Stomach pain, bloating, or gas

    • Nausea or vomiting

    • Diarrhea

    Other side effects, which are less common but might be more severe, could include:

    • Irregular heartbeat

    • Seizures

    • Persistent and severe diarrhea

    You should call your doctor if you notice any of these side effects, or if you develop any other new or concerning symptoms. Lactulose solution shouldn't be given to children under 14 years of age unless your doctor recommends it.

How to take Constulose

Your pharmacist will provide you with instructions on how to take your Constulose prescription. Be sure to read your prescription label and follow the instructions. Call your doctor or pharmacy if you have any questions.

Constulose can come in different forms and doses, so be sure to follow the specific instructions on your prescription. The starting dose of lactulose is typically 15 mL orally taken once daily for acute or chronic constipation. For hepatic encephalopathy, the starting dose is typically 30 mL orally taken three times a day.

If the initial dose produces diarrhea, tell your doctor. Your doctor may need to decrease your oral dosage.

What to avoid while taking Constulose

Constulose has 239 drug interactions. Don’t change what you are taking without checking with your doctor or pharmacist. That includes other medications or supplements, as well as over-the-counter drugs. 

Possible drug interactions with lactulose include:

  • Cymbalta (duloxetine)

  • Lasix (furosemide)

  • Lipitor (atorvastatin)

  • Tylenol (acetaminophen)

  • Synthroid (levothyroxine)

Ask your doctor for medical advice before drinking alcohol. Drinking too much alcohol can lead to an increased risk of persistent and severe diarrhea.

Medication alternatives to Constulose

If your healthcare provider prefers to put you on another treatment altogether, they may suggest another laxative in another drug class. Here are some common doctor-recommended alternatives based on your health issue:

  • Chronic constipation

    Dulcolax (bisacodyl)

    Lubiprostone (Amitiza)

    Plecanatide (Trulance)

  • Hepatic encephalopathy

    Xifaxan (rifaximin)


    Constilac (lactulose)

Constulose prescription FAQs

  • How much does Constulose cost?

    Depending on your pharmacy, Constulose oral solution (10 g/15 mL) costs around $15 for 237 mL without insurance. Fortunately, generic brands, such as lactulose, offer an affordable alternative.

  • How can I refill my Constulose prescription?

    To refill your Constulose prescription, book a virtual appointment with one of our top rated board-certified doctors. After reviewing your symptoms, your doctor can send an electronic prescription to your local pharmacy.

  • How long does it take Constulose to work?

    It may take up to 48 hours to have a normal bowel movement after your oral dose.

  • Who should not take Constulose?

    To make sure lactulose is safe for you, tell your doctor if you have:

    • Diabetes

    • If you're on a special low-galactose diet

    • If you need intestinal tests using a scope, such as a colonoscopy

    Diabetes mellitus patients should ask their doctor for medical advice before taking lactulose. Lactulose may be high in fat and carbs, and you'll need to work with your doctor to find an adequate lactulose dosage.

  • Should you drink water after taking Constulose?

    Yes, you should drink plenty of water after taking Constulose oral doses to prevent dehydration.

  • How many hours does Constulose take effect?

    After taking an oral dose, Constulose takes between 24 and 48 hours to take effect.

  • What happens if I miss a dose of Constulose?

    If you miss a dose of Constulose, take the missed dose as soon as you remember. Skip the missed dose if it’s almost time for your next dose. Avoid taking two doses to make up for a missed dose.

  • What happens if I take too much Constulose?

    If you've taken too much Constulose, seek emergency medical attention or contact your local poison control center.

3 simple steps to request your Constulose prescription today 

Step 1: Book an appointment

Step 1

Book a Constulose prescription request appointment.

Book a same day appointment from anywhere.

Step 2: Visit with a doctor on your smartphone

Step 2

Talk to your medical provider regarding your Constulose prescription.

Visit with a doctor on your smartphone or computer.

Step 3: pick up at local pharmacy

Step 3

Pick up your Constulose prescription.

We can send prescriptions to any local pharmacy.

How to talk to your doctor about Constulose (lactulose)

At Plushcare, our priority is making sure you receive the information and advice you need when making decisions about your health and wellness. Our board-certified doctors are here to help you every step of the way, focusing on genuine patient connection to help you feel confident and secure in your treatment journey.

The following are some questions to ask your doctor about Constulose and constipation treatments:

  • When should I become concerned about my constipation?

  • Are there any changes to my diet that I should make while on Constulose?

  • What should I do if I experience unwanted side effects?

  • If this medication doesn’t work for me, what other treatment options can we try?

  • Are there other fiber supplements or probiotics that might help with my symptoms?

  • Will any of my current medications negatively interact with Constulose?

  • How will we track my treatment for chronic constipation or Hepatic encephalopathy?

  • When should I schedule a follow-up appointment to discuss treatment results?

Constulose prescription pricing details

How pricing works

To get a new or refill on your Constulose prescription, join our monthly membership and get discounted visits.

Paying with insurance



First month free



30 days of free membership

  • Same-day appointments 7 days a week

  • Unlimited messages with your Care Team

  • Prescription discount card to save up to 80%

  • Exclusive discounts on lab tests

  • Free memberships for your family

  • Cancel anytime

Visit price with insurance

Often the same as an office visit. Most patients with in-network insurance pay $30 or less!

  • We accept these insurance plans and many more:

    • Humana
    • Aetna
    • Cigna

Paying without insurance



First month free



30 days of free membership

  • Same-day appointments 7 days a week

  • Unlimited messages with your Care Team

  • Prescription discount card to save up to 80%

  • Exclusive discounts on lab tests

  • Free memberships for your family

  • Cancel anytime

Visit price without insurance

Initial visits are $129.

Book an appointment

If we're unable to treat you, we'll provide a full refund.

Constulose prescription resources


PlushCare is dedicated to providing you with accurate and trustworthy health information.

PlushCare content is reviewed by MDs, PhDs, NPs, nutritionists, and other healthcare professionals. Learn more about our editorial standards and meet the medical team. The PlushCare site or any linked materials are not intended and should not be construed as medical advice, nor is the information a substitute for professional medical expertise or treatment.