Side Effects Of Milk Of Magnesia

December 16, 2023

Milk of magnesia is an oral suspension that contains hydrated magnesium carbonate. It is an over-the-counter medication intended for occasional or short-term use as an antacid or laxative. Women who are pregnant or breastfeeding should ask their physician before using milk of magnesia. Patients with kidney disease should check with their healthcare team to ensure this medication is safe for them to use. If symptoms persist for more than seven days, the patient should see a doctor before continuing this medication. Milk of magnesia is available as a chewable tablet and as a liquid. Individuals using the liquid formulation will need to shake the medicine before consuming it.

As mentioned, many individuals use milk of magnesia as an over-the-counter laxative and antacid. Thus, patients take milk of magnesia for constipation relief. This medication can provide heartburn relief, and it is also a treatment for indigestion and sour stomach. Some patients will try a milk of magnesia colon cleanse. In some cases, individuals will have access to a variety of milk of magnesia flavors. However, before taking it, patients must first understand the potential side effects of milk of magnesia.


Diarrhea is the most frequently reported side effect that patients experience after taking milk of magnesia. As a laxative, this medication increases the amount of water in the intestines to induce a bowel movement. It softens and moistens the stool. Most patients will have a normal bowel movement within six hours of taking a single dose of milk of magnesia. However, diarrhea could occur if an individual takes more than one dose in twenty-four hours or if the dose consumed exceeds the recommended amount on the product packaging. Diarrhea is defined as loose or watery stools. Patients may experience this symptom with abdominal pain or bloating.

If diarrhea occurs, patients should not take any additional doses of milk of magnesia. They should consult a doctor if nausea accompanies their diarrhea. It is often beneficial to eat a low-fiber diet and avoid dairy products until diarrhea resolves. Patients are also advised to drink plenty of fluids to prevent dehydration. If diarrhea continues for more than two days, patients may wish to consult a doctor. They may prescribe additional medication.

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Nausea And Vomiting

Milk of magnesia may irritate the stomach. This could trigger nausea and vomiting for some patients. These symptoms are more likely to occur in patients who need to take more than one dose to relieve their constipation. Doctors suggest that patients try to avoid strong odors or flavors to ease their nausea. It can also be helpful to go outside for fresh air. Some patients can relieve their nausea by eating peppermint or ginger, and eating bland food such as rice or crackers could be soothing for nausea as well.

If vomiting occurs, patients should note how many times they experience this and obtain emergency medical attention if the vomit is black or bloody. Emergency medical care is also necessary in cases where the patient cannot keep any food or liquid down at all.

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Abdominal Pain

Abdominal pain may occur as a side effect of milk of magnesia. It is also a common complication of constipation and upset stomach. The abdominal pain associated with laxative use may be experienced as a sharp, stabbing pain. Patients may also feel a dull or throbbing ache. This type of pain occurs most often in the lower abdomen. However, they may be present in several areas of the abdomen. Abdominal pain may indicate a bowel obstruction or another serious medical condition. Thus, patients should see a doctor if they experience severe pain, pain that persists, or pain that worsens in any way.

Emergency medical attention is necessary if the abdomen is swollen or tender to the touch. Patients should go to the emergency room if they have abdominal pain accompanied by bloody stools, fever, or persistent nausea and vomiting. Doctors will use a stethoscope to listen for bowel sounds in the patient's abdomen. They will press on the patient's abdomen to check for lumps and areas of pain. They may request imaging studies as well. Depending on the exact cause of the pain, patients may be treated with medications or surgery.

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Rectal Bleeding

Rectal bleeding can be a sign of hemorrhoids, anal fissures, or cancer. Individuals who experience this symptom should see a doctor urgently. Patients with rectal bleeding may notice blood on the toilet paper after having a bowel movement. There may also be drops of blood in the toilet bowl. The stool itself could be red or black. The doctor will begin with blood tests and a general physical examination to assess the patient for signs of anemia and abdominal pain or masses as part of assessing rectal bleeding. Next, they will perform a digital rectal examination to check for blood or masses in the rectum. Patients may also have a proctoscopy examination. Doctors may request a colonoscopy if more information is required.

If possible, patients may want to estimate how much blood loss they experience through rectal bleeding. This information helps guide the doctor in the assessment. It is beneficial for them to know how often the patient experiences rectal bleeding as well.

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Patients who take milk of magnesia on a long-term basis or at doses larger than the recommended levels could experience lightheadedness and dizziness. Patients who feel lightheaded could faint, and they are at a higher risk for falls and injuries. During an episode of lightheadedness, the patient should try to sit or lie down as soon as possible. Patients who experience this symptom while taking milk of magnesia should discontinue the use of it immediately.

It can be helpful for the patient to keep a journal of lightheadedness episodes so they can share this information with their doctor. To assess lightheadedness, doctors will perform a physical examination. Patients may need to have blood tests or imaging studies. This symptom may resolve on its own once milk of magnesia is stopped.

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Slow Heartbeat

A potential severe side effect linked to milk of magnesia is a slow heartbeat. This is a sign of a milk of magnesia overdose. Research indicates that this medication reduces potassium excreted from the body and increases the amount of magnesium in an individual's body. This can trigger an irregular heartbeat that is often slow. If patients deal with a slow heartbeat and are taking milk of magnesia, they should stop taking it right away. They should then seek immediate medical attention. It is likely that they will not be able to take milk of magnesia any longer due to this side effect. However, doctors will need to evaluate each patient and make that assessment.

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Muscle Weakness

Muscle weakness is a major sign that an individual have taken too much milk of magnesia. In other words, muscle weakness is a significant indication that individuals are dealing with abnormally high levels of magnesium in their body. Any individual taking milk of magnesia who experiences muscle weakness should immediately stop taking this substance. They will also need to receive emergency medical attention. Emergency treatment for patients who are dealing with muscle weakness, and therefore a milk of magnesia overdose, is vital to reverse the effects of milk of magnesia.

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Dry Mouth

Some individuals who take milk of magnesia can deal with dry mouth as a side effect. If they experience dry mouth when taking milk of magnesia, it is a sign that they are dehydrated. If dry mouth is mild, patients can likely continue taking milk of magnesia if they increase the amount of water they are drinking to compensate for the fluids they are losing. However, if patients are experiencing severe dry mouth, they should stop taking milk of magnesia and increase their water intake. In addition, severe dry mouth, and therefore severe dehydration, may require medical attention.

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Extreme Thirst

Extreme thirst when individuals are taking milk of magnesia is another side effect that indicates they are dealing with dehydration. Unfortunately, extreme thirst often means that affected individuals will need to stop taking milk of magnesia, at least on a temporary basis. Patients will also need to drink a significant amount of water to rehydrate their body. They should also maintain a higher water intake if they are able to resume taking milk of magnesia. Of course, some individuals with extreme thirst due to milk of magnesia will need to receive medical help to treat this symptom and their dehydration.

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Shallow Breathing

Shallow breathing is another potential side effect of milk of magnesia that indicates patients may have taken too much of it. The result of this, as mentioned previously, can be that patients now have abnormally high levels of magnesium in their body. As with the other side effects that indicate high magnesium, patients dealing with shallow breathing need to stop taking milk of magnesia right away. In addition to ceasing milk of magnesia, patients should also receive immediate medical attention to treat their shallow breathing effectively and thus, prevent lasting consequences from the high levels of magnesium and the side effects, like shallow breathing, that it causes.

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