Magnesium is an essential mineral for good health, contributing to everything from heart, brain, nerve, and muscle function, to blood sugar control, metabolism, and energy creation. But as with anything in life, you can have too much of a good thing! In this article, we explain how much magnesium is too much and how you can ensure that you’re taking the right amount.
NB: If you think you’ve overdosed on magnesium, it’s important to get medical attention immediately.
How much magnesium should you take?
Magnesium deficiency is quite common, prompting many people to take supplements to maintain adequate levels. You might also consider taking a supplement if you have certain health conditions that require more magnesium than the average person, such as:
- Chronic stress depletes magnesium levels and reduces absorption.
- Gastrointestinal disorders like Crohn’s disease, celiac disease, and ulcerative colitis, interfere with magnesium absorption.
- Kidney problems or type 2 diabetes, both of which can cause excess magnesium loss through increased urination.
- Pregnancy and breastfeeding, when you need enough magnesium for both yourself and your growing baby.”
According to the National Institutes of Health, the recommended dietary allowances (RDAs) for magnesium are as follows:
| Age | Male | Female |
|---|---|---|
| Birth to 6 months | 30 mg* | 30 mg* |
| 7–12 months | 75 mg* | 75 mg* |
| 1–3 years | 80 mg | 80 mg |
| 4–8 years | 130 mg | 130 mg |
| 9–13 years | 240 mg | 240 mg |
| 14–18 years | 410 mg | 360 mg |
| 19–30 years | 400 mg | 310 mg |
| 31–50 years | 420 mg | 320 mg |
| 51+ years | 420 mg | 320 mg |
*Adequate Intake (AI)
Can you overdose on magnesium?
First, let’s clarify what’s meant by an overdose. Whether you’re taking 401mg of magnesium or 10,000mg, you’re technically overdosing according to the medical definition. But if we’re talking about an overdose that leads to poisoning, the threshold is very, very high for a magnesium overdose.
Toxicity, or poisoning, generally occurs at doses above 5,000mg of magnesium per day. If your supplement contains 350mg of magnesium, then, you’d have to take at least 14 doses — a two-week supply — in one day. So while it’s absolutely possible to overdose on magnesium, it’s not something you’d really come even close to doing if you took your supplements as recommended.
But what about if you wanted to take, say, 600mg of magnesium a day? That’s 200mg more than the recommended upper intake, but it doesn’t put you anywhere near the 5,000mg region you’d need to have a serious reaction. In fact, some people routinely take higher doses, e.g. 500-600mg for migraines (although it’s worth noting that this is usually done under a doctor’s advice and supervision).
So going over 400mg isn’t necessarily harmful to a healthy person, but what it could do is cause you some uncomfortable side effects. The most common are diarrhea, nausea, bloating, and stomach cramps. The likelihood of experiencing these side effects increases as you pass 375-400mg of magnesium, but they can quickly be resolved by simply lowering your dose. You can also reduce the likelihood of side effects by taking a highly bioavailable, well-absorbed type of magnesium, such as taurate, glycinate or malate, rather than magnesium oxide or citrate.
Difficult doesn’t mean impossible…
While the threshold for magnesium toxicity is high, overdose is still a possibility and can have serious consequences. Some people are more at risk than others…
People with kidney disease or kidney failure – Earlier, we mentioned that kidney problems can cause you to lose too much magnesium in your urine. It’s important to know that the opposite can happen, too. Healthy kidneys are great at regulating magnesium levels, but if they’re not working properly, magnesium can build up to dangerously high levels. This is called hypermagnesemia.
Pregnant women being treated for pre-eclampsia – This condition involves dangerously high blood pressure that puts the life of both mother and baby at risk. The standard treatment involves incredibly high doses of magnesium, and your medical team will often monitor you to prevent hypermagnesemia. Make sure they know if you’re taking magnesium supplements as they will more than likely need you to stop.
People with heart disease, some gastrointestinal conditions, and thyroid disease may also be more vulnerable to magnesium toxicity. That’s why we always say: if you have health problems, speak to your doctor before taking magnesium supplements to be on the safe side!
What if you’ve taken too much magnesium?
Signs that you may have taken too much magnesium include:
- Diarrhoea
- Nausea or vomiting
- Muscle weakness
- Lethargy
- Facial flushing
- Urine retention
- Confusion or disorientation
- Dizziness
- An irregular heartbeat
If you think you’re experiencing a magnesium overdose, it’s important to get medical attention immediately. Serious overdose can cause low blood pressure, abnormal heart rhythm, cardiac arrest (when the heart stops), and respiratory arrest (when breathing stops). Treatment might involve diuretics to help you get rid of the excess magnesium in your urine, or an intravenous calcium drip to help counter the magnesium’s effects.
The bottom line
To summarise, it’s very difficult to accidentally overdose on magnesium thanks to its high toxicity level. However, it’s not impossible, and some people are more at risk of overdose than others. You could also experience uncomfortable side effects if you stray too far past the recommended upper limit.
We want everyone to experience the great well-being benefits of magnesium, but we want you to do it in the safest way possible! That means always sticking to the recommended dosage unless you’ve discussed it with your doctor first.
