If you want a simple rule:
-
Glycinate is often chosen for better stomach tolerance and “general” supplementation.
-
Citrate is often chosen when the goal is constipation support, because it can loosen stools.
-
Oxide is often the cheapest and widely available, but it’s commonly considered less absorbable than some other forms and may cause more digestive side effects in some people.
The “best” magnesium is the one that matches your goal and your tolerance, while staying within safe supplemental limits.
Why magnesium form matters
Many people think magnesium is “one supplement,” but the form changes:
-
how well it dissolves
-
how well it’s absorbed
-
how likely it is to cause diarrhea or stomach upset
-
how useful it is for a specific target (like constipation)
Also, labels can be confusing because you’ll see two numbers:
-
The compound amount (e.g., magnesium citrate 1000 mg)
-
Elemental magnesium (the actual magnesium your body uses)
Elemental magnesium is the number that matters most for dosing.
Glycinate vs Citrate vs Oxide (fast comparison)
Here’s the practical comparison most readers want:
1) Magnesium glycinate
What it is: Magnesium bound to glycine (an amino acid).
Why people choose it: Often better tolerated and less likely to cause diarrhea compared with some forms.
Best for:
-
general magnesium support
-
people with sensitive digestion
-
people who want magnesium without laxative effects (for many users)
Possible downside:
-
can be more expensive than oxide
2) Magnesium citrate
What it is: Magnesium bound to citric acid.
Why people choose it: It tends to dissolve well and is commonly used when constipation is part of the goal.
Best for:
-
occasional constipation support
-
people who want a form more likely to affect bowel movements
Possible downside:
-
more likely to cause loose stool/diarrhea, especially at higher doses or for sensitive people
3) Magnesium oxide
What it is: Magnesium bound to oxygen.
Why people choose it: Widely available and often low-cost.
Best for:
-
budget-friendly options
-
people who tolerate it well
Possible downsides:
-
commonly considered less absorbable than some more soluble forms
-
may cause more GI upset in some people
Which magnesium should you choose? (based on your goal)
Instead of chasing a “best overall,” choose based on your main goal:
Goal A: “I want general magnesium support”
Start with: Glycinate
Why: many people tolerate it well and can stick with it consistently.
Alternative: Citrate (if your digestion is stable and you’re okay with mild stool-softening).
Goal B: “I’m constipated”
Start with: Citrate (or another form commonly used for bowel support)
Why: citrate can pull water into the intestines and help bowel movement for some people.
Important caution:
If you are constipated for weeks, have severe pain, blood in stool, unexplained weight loss, or you rely on laxatives frequently, you should seek medical evaluation.
Goal C: “I want magnesium for sleep”
Often chosen: Glycinate
Why: people prefer it because it’s typically gentler on the stomach and doesn’t “force” bowel effects at night.
Reality check: Sleep benefits are not guaranteed. Magnesium may help more if your intake is low or stress/tension is a factor.
Goal D: “I want fewer side effects”
Most common choice: Glycinate
If citrate gives you diarrhea or cramps, glycinate is often tried next.
Goal E: “I want the cheapest option”
Most common option: Oxide
But if oxide upsets your stomach or doesn’t seem helpful, switching to a different form may improve tolerance and consistency.
How to read a magnesium label (so you don’t overdo it)
This is where many people get confused.
Step 1: Find “elemental magnesium”
The label might show:
-
“Magnesium (as magnesium glycinate) — 120 mg” ✅ (this is elemental magnesium)
or it might show the compound weight separately.
Always dose by elemental magnesium unless your clinician advises otherwise.
Step 2: Respect safe supplemental limits
For many adults, the tolerable upper limit for magnesium from supplements/medications is often cited as 350 mg/day (this limit is about side effects like diarrhea).
This does not apply to magnesium from food.
If you’re using magnesium for a medical reason that requires higher doses, it should be supervised.
Step 3: “Start low, go slow”
A smart approach:
-
Start with a smaller dose
-
Keep it consistent for 1–2 weeks
-
Adjust only if needed and tolerated
Timing: morning or night?
There’s no universal “best time.” Use logic:
-
If magnesium makes you feel calmer or sleepier → try evening
-
If it affects your stomach/bowels → take with food and consider earlier timing
-
If you’re splitting the dose → morning + evening can reduce side effects
Consistency matters more than the exact clock time.
Side effects: what’s normal and what’s not
Common side effects
-
loose stool / diarrhea (more common with citrate, higher doses, or sensitive digestion)
-
abdominal cramping
-
nausea
Red flags (stop and seek medical advice)
-
severe weakness, confusion, very low blood pressure symptoms
-
persistent vomiting
-
irregular heartbeat sensations
-
symptoms that worsen quickly
These are uncommon with typical doses in healthy people, but risk increases with kidney impairment or high-dose use.
Drug interactions (very important)
Magnesium can affect absorption of certain medications (especially some antibiotics and osteoporosis medications). Also, some drugs can change magnesium levels (like certain diuretics or long-term acid-suppressing meds).
Rule: If you take daily prescription meds, ask a pharmacist about:
-
whether magnesium interacts with your medication
-
how many hours to separate doses
Mini decision guide (choose in 20 seconds)
Pick glycinate if:
-
you want general support
-
you have a sensitive stomach
-
you want fewer laxative effects
Pick citrate if:
-
constipation is a main issue
-
you don’t mind possible stool loosening
Pick oxide if:
-
budget matters
-
you tolerate it well
(If it causes stomach upset or doesn’t suit your goal, switch.)
FAQs
Is glycinate “better absorbed” than citrate?
Both are commonly considered more soluble than oxide, and many people choose them for better tolerance/absorption patterns. But individual response varies—your digestion and consistency matter.
Can I take magnesium every day?
Many people do, but food-first is best. If using supplements, keep dose reasonable and reassess regularly—especially if you’re taking medications.
Why does magnesium citrate cause diarrhea?
Because it can draw water into the intestines, which can soften stool and speed bowel movements.
Is magnesium oxide “bad”?
Not necessarily. Some people do well on it. The main issues are that it may be less absorbable than some forms and more likely to cause GI effects for some users.
Should I choose magnesium based on “elemental magnesium”?
Yes. Elemental magnesium is what matters for dosing.
Sources
-
NIH – Office of Dietary Supplements: Magnesium (Health Professional Fact Sheet)
-
NIH – Office of Dietary Supplements: Magnesium (Consumer Fact Sheet)
-
NIH – Office of Dietary Supplements: Dietary Supplements — What You Need to Know
