Magnesium on Keto: Are You Getting Enough?
Quick answer: Maybe not, and keto isn't the only reason. Reviews of US intake find a large share of people already eat less magnesium than the average requirement before they change anything. On keto, the fix starts on your plate: leafy greens, plus nuts and seeds that fit your carbs. KetoDick's rule is that magnesium pills are a conversation with your doctor first, not something you self-prescribe (video lbRPlGZ3Rvw).
On this page
- How much magnesium you need
- Why so many people come up short
- What keto changes
- Where to get it on keto
- Why a blood test may not settle it
- What the research says
- KetoDick's take
- When to involve your doctor
- Key takeaways
- Related
How much magnesium you need
The NIH Office of Dietary Supplements puts the adult recommended daily amount at 310 to 320 mg for women and 400 to 420 mg for men (NIH ODS). Those figures go back to the Institute of Medicine's reference intakes (IOM 1997).
There's also an upper limit of 350 mg a day, and here's the detail people miss: that limit is for magnesium from supplements, not from food (NIH ODS). Spinach doesn't have a cap. Pills do.
That one detail tells you a lot about where to start.
Why so many people come up short
A review of US magnesium status found that a large share of the population eats less magnesium than the estimated average requirement (Rosanoff 2012). The average requirement is a lower bar than the recommended amount, so falling short of it means a real gap, not a rounding error.
In other words, a lot of people starting keto were probably low before the first bacon-and-eggs breakfast. Keto didn't create the problem. It can make it worse or better depending on what you put on the plate.
What keto changes
Two things pull in different directions.
The worse direction: if you treat carbs like the enemy and avoid vegetables, you cut some of the best magnesium sources along with the bread. KetoDick has a line for this: people get themselves into keto-flu trouble by looking at lettuce like it's the devil (from the video lbRPlGZ3Rvw). In one study of women on different diets, the Atkins group had shifted toward inadequate intake for several nutrients by week eight, magnesium among them (Gardner 2010). The other diets in that study had their own shortfalls.
The better direction: dropping processed starches frees up carbs to spend on greens. That's his whole "spend your carbs" idea. Lettuce and arugula are carbs, but you get a huge volume for very few grams, and greens bring calcium and magnesium along with them (video 1vyxuWlxT5M).
Where to get it on keto
So what you do is build magnesium into meals you're already eating.
- Leafy greens first. He names baby spinach as a calcium source and says magnesium is pretty common in green leafy vegetables (video lbRPlGZ3Rvw).
- Nuts and seeds, counted. They fit keto in modest portions, but they add carbs and calories fast, so they go in your tracker. See Do Nuts Kick You Out of Ketosis?.
- Hide the greens. He puts arugula under steak with gravy, and cooks vegetables in seasoned oil, bacon fat or butter so they taste like something (video 1vyxuWlxT5M).
- A multivitamin as a backstop. In the 2018 beginners' video he suggests a common multivitamin that includes magnesium and calcium, with no brand push (video UygKGoP_BtA). Whether multivitamins do much is its own question: Do Multivitamins Actually Work?.
A sports drink won't do this job. See Are Sports Drinks Good for Electrolytes on Keto?.
Why a blood test may not settle it
You might think: I'll just get my magnesium checked. Reasonable, but the same review notes that serum magnesium, the standard blood number, is an insensitive marker of status (Rosanoff 2012). Most of your magnesium isn't in your blood, so a normal result doesn't prove you're well stocked.
That's not a reason to skip the test. It's a reason to look at your food log too, and to talk through both with your doctor.
What the research says
- Reference amounts: adult RDA 310 to 320 mg for women, 400 to 420 mg for men; upper limit 350 mg a day from supplements only (NIH ODS; IOM 1997).
- US intake: a large share of people eat less than the average requirement, and serum magnesium is a weak status marker (Rosanoff 2012).
- Health links: in cohort studies, each extra 100 mg a day of magnesium was associated with lower risk of heart failure, stroke, type 2 diabetes and death from any cause, though not of total coronary heart disease (Fang 2016). That's association, not proof that adding magnesium causes the drop; see Observational vs RCT.
- Low-carb diets: at eight weeks, women on Atkins moved toward inadequacy for thiamine, folate, vitamin C, iron and magnesium (Gardner 2010).
One caveat on the NIH page: the figures here were read from search snippets, not the page itself, so check the current page before quoting its numbers.
None of these studies tested keto-specific magnesium supplementation. The case for greens-first is food sense plus the supplement-only upper limit, not a keto trial.
KetoDick's take
He names magnesium as one of the four electrolytes to think about on keto, alongside sodium, potassium and calcium (video lbRPlGZ3Rvw). His preferred source for calcium and magnesium is leafy greens, and he says that repeatedly (videos lbRPlGZ3Rvw, 1vyxuWlxT5M).
He's equally clear that pills are different. Potassium and magnesium supplements can have kidney effects that eventually reach the heart, so he says not to start them prematurely, without a deficiency problem, or without your doctor in the conversation (video lbRPlGZ3Rvw). He repeats the doctor-first rule when he talks about keto flu (video 9r2Y74AnjUQ).
The deficiency signs he lists for electrolytes in general are headaches, cramping, irritability and low energy (video lbRPlGZ3Rvw). Those overlap with plenty of other causes, which is one more reason to check with someone who can test you. Cramps in particular get their own post: Leg Cramps on Keto.
When to involve your doctor
- Before any magnesium supplement, full stop, by his rule (video lbRPlGZ3Rvw).
- Kidney disease or reduced kidney function. Kidneys clear excess magnesium. He notes that many people with pre-diabetes or type 2 diabetes have some kidney impairment, even if no one has told them (video lbRPlGZ3Rvw).
- Heart history, for the same reason he gives above (video lbRPlGZ3Rvw).
- If you take other medications, since he says anyone on medication should expect dosing questions when starting keto (video UygKGoP_BtA). See Medications.
Key takeaways
- Adult targets are roughly 310 to 320 mg a day for women and 400 to 420 mg for men.
- A large share of US adults are below the average requirement before keto starts.
- Keto helps if you spend carbs on greens, and hurts if you avoid vegetables.
- The 350 mg upper limit applies to supplements, not food, so food comes first.
- A normal blood magnesium doesn't prove you're well stocked.
- Supplements go through your doctor, especially with kidney or heart history.