MiraLax Not Working After 3 Days: 5 Causes (Dr. Farahat)

Our content is not intended nor recommended as a substitute for medical advice by your doctor. Use for informational purposes only.


What you need to know:

Common causes of MiraLax not working for 3 days are poor diet and lifestyle, medications that cause constipation, or the presence of another disease that causes constipation. The table below summarizes the causes of MiraLax nonresponse after 3 days:

The cause of non-response to MiraLax Notes
1- DIET: – Low fiber diet
– Eating less in general (not stool bulk).
– Not drinking enough water.
2- Your Lifestyle. – Sedentary lifestyle (no activity or no exercise).
– Not training your bowel by defecating after meals.
3- Wrong MriaLax use. – Smaller-than-recommended dose.
– Irregular use of MiraLax.
– Not drinking enough water with Miralax.
4- Miralax is not your fit. – Osmotic laxatives (as MiraLax) don’t fit all types of constipation.
– Your doctor may add another laxative or shift to another type of MiraLax.
5- Alternate cause of constipation – You may be taking a drug that causes constiaption.
– Having a disease affecting the nerves of your colon (as DM).
– Having a brain or spinal cord disease.
– having an endocrinal disease (as hypothyroidism) and others.


1- Diet.

The fiber in the diet is very important for improving your constipation. A diet that is low in fiber may counter can counter the effect of MiraLax. Also, The amount of food you eat matters. If you have a Poor appetite for any reason, you will eat less. Lack of stool bulk (due to eating less) may cause MiraLax to fail. Fibers are of two types, soluble (dissolve in water and forms a gel), and insoluble (cannot dissolve in water). Soluble fibers that dissolve in water are able to retain water inside your colon. This helps to soften the poop (reference). And Consequently, improvement of constipation and better action of MiraLax. In conclusion, when you have no bowel movement after 3 days of Miralax, Ask  yourself 2 questions:

  • Is my diet high or Low in fiber?
  • Do I obtain enough amounts of food or not?

A diet that is low in fiber or failure to obtain enough food amount may be the cause of Non-response to MiraLax.

Examples of Low-fiber diets that may be your Problem:

  • Processed (refined) grains.
  • High protein diet (red meat).
  • Milk and dairy products.
  • Fried and fast foods.
  • Alcoholo.

The recommended daily fiber intake is about 25-30gm of fibers (reference). Exceeding the recommended amount may produce side effects such as bloating and cramps.

Examples of High fiber diets to try:

  • Whole-grain cereals, bread, and pasts (whole grain has resistant soluble fibers that are good for constipation).
  • Prunes and prune juice are best for constipation due to their high soluble fiber content.
  • Apples and pears.
  • Kiwi
  • Figs.
  • Spinach, and other greens.
  • Beans, Peas, and lentils.

NOTE: if your constipation is due to IBS, Some of the above foods may not be suitable for you. Some of the above foods are high in FODMAP (highly fermentable sugars that worsen your IBS symptoms). Please check this article about the best high fiber fruits for IBS.

2- Your lifestyle.

Common causes of non-response to non-response:

  • Bed-ridden people (elderly, debilitating diseases).
  • extensive psychological stress (reference).
  • Lack of physical activity (walking, exercise, running).
  • Decreased water intake (dehydration).
  • Not training your bowels: Training your bowel by going to the toilet every time you eat a large meal is the best time to produce a bowel movement.

being physically active, living a less stressed life, and staying hydrated improves the response to MiraLax.

3- Alternate cause of constipation.

Constipation is usually due to either IBS-predominant constipation or chronic idiopathic constipation. However, Many diseases and drugs can also cause constipation. The presence of an alternate cause of constipation can be the reason why MiraLax is not working for 3 days or more. A summary of the causes of constipation (other than IBS-C and chronic idiopathic constipation): 1- Diseases affecting the nerves supplying your colon:

  • Diabetes mellitus.
  • Autonomic nerve neuropathy (weakness of sympathetic and parasympathetic nerves that is responsible for your colon motility).
  • Other less common causes such as Hirschsprung disease and intestinal pseudo-obstruction.

2- Other neurological diseases.

  • Multiple sclerosis.
  • Spinal cord injury.
  • Having Parkinson’s disease.

3- Drugs. Drugs are a commonly overlooked cause of constipation. Taking a constipation-inducing medication may lead to the failure of MiraLax to produce bowel movements. Always review your list of medications for drugs causing constipation such as (reference):

  • Analgesics such as opioids and Non-steroidal anti-inflammatory drugs.
  • Drugs used in neurological and psychological diseases (anti-psychotics, Tricyclic anti-depressants, and antiparkinson drugs).
  • Iron supplements.
  • Antacids that contain (aluminum hydroxide).
  • Anti-spasmodics (used for abdominal pain).
  • Some antihypertensive medications such as calcium channel blockers (amlodipine).
  • Others.

The list of medications that can cause constipation is long. Please consult your doctor or nurse if you have any medications. The answer to the cause of non-response to MiraLax may be your chronic medications. 4- Endocrinal diseases.

  • Diseases of your thyroid gland (especially hypothyroidism).
  • Hypercalcemia (excess calcium due to a disease or overdosage of calcium supplements or calcium-containing antacids).
  • Pregnancy.

5- Others

  • diseases of the anorectum such as fissures, tumors, or strictures.
  • Psychological diseases such as depression and anxiety.
  • Other rare conditions such as amyloidosis, systemic lupus erythematosus.

The point of enlisting all these causes is to make you aware of them. Not all constipation is due to IBS, or chronic idiopathic constipation. So, the non-response to MiraLax for 3 days or more may indicate an alternate cause of constipation. The diagnosis of such conditions often requires complex evaluation by your doctor. Consult your doctor if you suspect alternate causes of your constipation such as drugs.

4- The way you use MiraLax.

Faulty use of MiraLax can be responsible for its failure to produce a bowel movement. Common pitfalls during the use of MiraLax:

  • Taking a sub-therapeutic dose: The usual dose of MriaLax is 17 grams of powder in 8 ounces of water once daily. Taking a smaller dose or not taking it every day cause the non-response.
  • Not drinking enough water with MiraLax powder.
  • Abuse of MiraLax for very long periods with large doses (your colon becomes less responsive to laxatives).

5- MiraLax is not your fit.

MiraLax belongs to the osmotic laxative category. we – doctors – treat constipation according to its mechanism. for example:

  • Secondary constipation (constipation that occurs secondary to drugs or diseases) is usually treated by eliminating the primary causes.
  • Primary constipation can occur by different mechanisms such as normal transit constipation, colon inertia, pelvic muscle dyssynergia, or output delay (Learn more).
  • For each type of constipation, a specific type of laxative (or a combination of laxatives) works best.
  • So, Osmotic laxatives (as MiraLax) may not be the right type for your constipation.
  • Consulting your doctor is a must to determine the best fit for you.

Your doctor may decide to add another laxative (such as stimulant laxatives like Dulcolax (bisacodyl)).

Miralax Poop Chart.

No Urge to Poop in 3 Days: When to Worry.