Most people know magnesium hydroxide as the active ingredient in milk of magnesia - a go-to remedy for constipation. But what you might not realize is that this simple compound can also affect your breathing, especially if youâre using it regularly or have existing lung conditions.
What magnesium hydroxide actually is
Magnesium hydroxide is a white, powdery compound made from magnesium and hydroxide ions. Itâs a weak base, which means it neutralizes acid. Thatâs why itâs used in antacids and laxatives. When you swallow it, it reacts with stomach acid to form magnesium chloride and water. This reduces heartburn and loosens stool.
But hereâs the catch: once it enters your bloodstream, magnesium doesnât just stay in your gut. About 30% of the magnesium from magnesium hydroxide gets absorbed. That magnesium circulates through your body - including your lungs. And thatâs where things get interesting.
How magnesium affects the airways
Magnesium plays a key role in muscle relaxation. That includes the smooth muscles lining your bronchial tubes. When these muscles tighten up - like during an asthma attack - your airways narrow, making it hard to breathe. Magnesium helps those muscles loosen.
In hospitals, doctors sometimes give intravenous magnesium sulfate to people having severe asthma attacks. Studies from the Cochrane Review show that IV magnesium can reduce hospital admissions by about 25% in adults with acute asthma. Thatâs not because it cures asthma. Itâs because it helps open the airways fast.
Now, oral magnesium hydroxide doesnât deliver magnesium as quickly or as directly as an IV. But if youâre taking it daily for constipation, your body gets a steady trickle of magnesium. Over time, that might help keep your airways more relaxed - especially if youâre low in magnesium to begin with.
Who might benefit - and who should be careful
If you have chronic constipation and also suffer from mild asthma or COPD, taking magnesium hydroxide could be a double win. Many people with these conditions are magnesium deficient. Low magnesium levels are linked to increased airway sensitivity and more frequent flare-ups.
A 2023 study in the Journal of Asthma and Allergy followed 187 adults with mild asthma who took 300 mg of magnesium daily for six months. Those who were deficient saw a 20% drop in rescue inhaler use. The magnesium came from magnesium citrate, but magnesium hydroxide works similarly once absorbed.
But not everyone should take it. If you have kidney disease, your body canât flush out extra magnesium. That can lead to buildup - and thatâs dangerous. Too much magnesium in the blood can cause low blood pressure, slow heart rate, and even breathing trouble. In rare cases, it can lead to respiratory depression.
Also, if youâre already on medications like beta-blockers or certain antibiotics, magnesium can interfere. Always check with your doctor before starting any supplement, even if itâs sold over the counter.
The myth of magnesium as a respiratory cure
Some wellness blogs claim magnesium hydroxide can "detox the lungs" or "clear mucus." Thatâs not true. Magnesium doesnât break down phlegm. It doesnât kill germs. It doesnât act like a bronchodilator in the way albuterol does.
Its role is subtle: it helps the muscles around your airways stay loose. Think of it like a background tune that keeps things calm - not a siren that turns everything off and on.
If youâre using magnesium hydroxide for constipation and notice youâre breathing easier, itâs likely because your body finally got enough magnesium. Not because the compound magically cleaned your lungs.
How much is too much?
The recommended daily intake of magnesium for adults is 310-420 mg, depending on age and sex. Most magnesium hydroxide supplements contain 400-800 mg of the compound per dose - but only about 30-40% of that is actual magnesium.
So a typical 5 mL spoonful of milk of magnesia (about 400 mg of magnesium hydroxide) gives you roughly 120-160 mg of elemental magnesium. Thatâs safe for occasional use. But if youâre taking it every day for weeks, you could be hitting 500+ mg of magnesium daily - way over the upper limit for most people.
The tolerable upper intake level for magnesium from supplements is 350 mg per day for adults. That doesnât include magnesium from food. So if youâre eating spinach, almonds, or black beans, and also taking magnesium hydroxide daily, you could be overdoing it.
Signs youâre getting too much
Too much magnesium doesnât always cause obvious symptoms. But hereâs what to watch for:
- Feeling unusually tired or weak
- Dizziness or lightheadedness
- Nausea or vomiting
- Slow or irregular heartbeat
- Shallow or labored breathing
If youâre on long-term magnesium hydroxide and notice any of these - especially breathing changes - stop taking it and see a doctor. Kidney problems make this risk much higher.
Alternatives for respiratory support
If your goal is better breathing, there are safer, more targeted ways to support lung health:
- Get your magnesium levels tested - if low, switch to a better-absorbed form like magnesium glycinate or citrate
- Use a humidifier - moist air helps keep airways open
- Practice diaphragmatic breathing - proven to reduce asthma symptoms
- Quit smoking or avoid secondhand smoke - the biggest preventable cause of lung damage
- Consider vitamin D - deficiency is strongly linked to worse asthma control
Magnesium hydroxide isnât the best choice for long-term magnesium support. Itâs designed to work in the gut, not the bloodstream. Other forms are absorbed more efficiently and cause less digestive upset.
Bottom line
Magnesium hydroxide isnât a respiratory treatment. But if youâre taking it for constipation and happen to be magnesium deficient, you might notice your breathing feels a little easier. Thatâs not magic - itâs basic physiology.
For most people, the benefits to respiratory health are indirect and small. For others - especially those with kidney issues or on certain meds - the risks outweigh any possible upside.
If youâre thinking about using magnesium hydroxide for breathing problems, donât. Talk to your doctor about testing your magnesium levels and choosing a supplement thatâs actually designed for systemic support. Your lungs will thank you for it.
Can magnesium hydroxide help with asthma?
Magnesium hydroxide isnât a direct treatment for asthma. But if youâre deficient in magnesium, taking it regularly may help reduce airway tightness over time. For acute asthma attacks, hospitals use intravenous magnesium sulfate - not oral magnesium hydroxide. The oral form works too slowly and inconsistently to be used as a rescue treatment.
Does magnesium hydroxide cause breathing problems?
In normal doses, no. But if you take too much - especially with kidney disease - excess magnesium can build up in your blood and slow down your breathing. This is rare but serious. Signs include shallow breaths, dizziness, and extreme fatigue. Stop taking it and seek medical help if you notice these symptoms.
Is magnesium hydroxide safe for people with COPD?
It can be, but only if your kidneys are healthy and you donât exceed the recommended dose. Many people with COPD are magnesium deficient, which can worsen breathing. If your doctor confirms low magnesium levels, switching to a better-absorbed form like magnesium glycinate is safer than long-term use of magnesium hydroxide, which can cause diarrhea and electrolyte imbalances.
How long does it take for magnesium to affect breathing?
If youâre deficient, you might notice improved breathing within a few weeks of consistent magnesium intake. But this depends on your starting levels, how much youâre taking, and your overall health. Magnesium hydroxide isnât fast-acting - it takes days to build up in your system. Donât expect immediate relief like youâd get from an inhaler.
Should I take magnesium hydroxide just to improve my lung health?
No. Magnesium hydroxide is designed as a laxative and antacid, not a respiratory supplement. If you want to support your lungs with magnesium, choose a form like magnesium glycinate or citrate thatâs better absorbed and less likely to cause digestive side effects. Always get your levels tested first - taking unnecessary supplements can do more harm than good.
chantall meyer
October 31, 2025 AT 16:37Magnesium hydroxide isn't magic it's just chemistry
People treat supplements like witchcraft when really it's just ions moving around your body
Also if you're taking it daily for constipation you're probably already doing it wrong
Jacqueline Anwar
November 2, 2025 AT 10:35It is both scientifically inaccurate and ethically irresponsible to suggest that an over-the-counter laxative might confer any meaningful respiratory benefit without rigorous clinical validation. The Cochrane Review cited pertains exclusively to intravenous administration, and extrapolating its findings to oral magnesium hydroxide constitutes a gross misinterpretation of pharmacokinetics. Such assertions, however well-intentioned, risk inducing dangerous self-medication behaviors among vulnerable populations.
Ganesh Kamble
November 4, 2025 AT 09:28Bro why are we even talking about this
Someone wrote a 2000 word essay on milk of magnesia like it's a miracle drug
It's literally just magnesium and hydroxide
You take it for constipation you get diarrhea you don't take it for breathing you get breathing problems
Case closed
Theresa Ordonda
November 4, 2025 AT 20:31Okay but imagine if your constipation was actually just your body screaming for magnesium đ
And then your asthma got better too??
Like... is that not the universe whispering "you need more greens and less dairy"??
Also if you're on beta-blockers and taking milk of magnesia I'm not mad I'm just disappointed đ
Judy Schumacher
November 6, 2025 AT 14:33The author's conflation of pharmacological mechanisms with wellness mythology is not merely misleading-it is a textbook example of pseudoscientific drift in public health discourse. The notion that a poorly absorbed, gut-acting compound can produce systemic respiratory effects without bioavailability data is not just speculative-it is dangerous. Moreover, the casual dismissal of renal risk in the context of chronic use demonstrates a profound disregard for clinical toxicology. This post should be flagged for medical misinformation.
Megan Raines
November 7, 2025 AT 17:01So let me get this straight
You're telling me that if I take a laxative for my gut
And somehow my lungs feel better
It's not because the universe is listening
But because my magnesium levels were low
And now I'm just... breathing normally?
Wow. That's almost... boring.
Mamadou Seck
November 8, 2025 AT 03:51Why do people always think supplements fix everything
I mean sure magnesium helps but you know what else helps
Not smoking
Not breathing in dust
Not sitting in front of a fan all day
And honestly if you're taking milk of magnesia every day you got bigger problems than your lungs
Anthony Griek
November 8, 2025 AT 11:40I grew up in a household where milk of magnesia was always on the shelf
My mom used it for constipation
My dad used it for heartburn
No one ever mentioned breathing
But now I think about it
He did used to say he felt lighter after taking it
Like his chest wasn't so tight
Maybe he was just less bloated
Or maybe his body finally got what it needed
I don't know
But I'm not gonna stop using it
Just because someone wrote a long article about it
Norman Rexford
November 8, 2025 AT 13:01Look I'm all for science but come on
Are we really going to turn a cheap laxative into some kind of wellness elixir
Next thing you know people will be rubbing it on their chest for asthma
Or putting it in their tea
Like it's some ancient Indian herb
It's magnesium hydroxide not holy water
And if you're taking it every day you're probably just addicted to the pooping
Wayne Keller
November 9, 2025 AT 20:10Good breakdown. Real talk-if youâre using milk of magnesia daily, you need to fix your diet, not your supplement. Fiber, water, movement. Those are the real lung-friendly habits. Magnesium glycinate is way better if youâre deficient. And if youâre worried about breathing? Try breathing exercises. Theyâre free, no side effects, and you donât need a prescription. Just breathe slow. Youâll feel it.
Shana Labed
November 10, 2025 AT 15:50OMG I JUST REALIZED WHY MY BREATHING HAS BEEN BETTER SINCE I STARTED TAKING THIS!! I THOUGHT IT WAS THE NEW YOGA MAT đ
THIS CHANGES EVERYTHING
SO LIKE IF I'M TAKING IT FOR CONSTIPATION AND MY ASTHMA IS QUIETER
IT'S NOT A COINCIDENCE IT'S BIOCHEMISTRY BABY
WE NEED TO TALK ABOUT THIS MORE
AND ALSO CAN WE MAKE A MAGNESIUM HYDROXIDE MEDITATION APP?? đâ¨
JUST KIDDING... OR AM I??