Supplements for Water Retention: What Reddit Recommends vs. What the Labels Say

The supplements with the most consistent research behind them for water retention are magnesium (200–400 mg/day) and vitamin B6 (studied up to 100 mg/day, specifically for PMS-related bloating). Dandelion extract is the most heavily marketed "natural diuretic," but it's backed by one small, older study, not large clinical trials. Potassium helps too, but it's safer sourced from food than from a supplement bottle.

Here's what the actual evidence says behind each ingredient commonly recommended for water retention, where the real safety limits are, and when persistent swelling is a reason to see a doctor instead of buy a supplement.

What does the actual research say about each ingredient?

Water retention supplements, by evidence strength

Ingredient	Studied dose	Evidence strength	Caveat
Magnesium	200–400 mg/day (~250 mg for PMS bloating)	Moderate — several PMS-focused trials	Can cause loose stool at higher doses
Vitamin B6	Up to 100 mg/day (PMS studies)	Moderate — systematic review of 10 studies	High doses linked to nerve damage; don't exceed 100 mg without guidance
Potassium	From food, not supplements	Mechanistically sound, food-based evidence	Excess supplemental potassium is genuinely risky
Dandelion extract	Not standardized	Weak — one small 17-person study	Folk-medicine use, not clinical-trial-backed

Why does dandelion extract show up in every "natural diuretic" blend?

Mostly tradition, not trial data. Dandelion has a long history in folk medicine as a diuretic, and the study most commonly cited to support it is small: 17 people took three doses of dandelion leaf extract over 24 hours and showed a measurable increase in urine output. That's a real result, but it's one small study with no placebo-controlled follow-up at scale — enough to explain why dandelion is in nearly every over-the-counter "water pill" blend, not enough to call it clinically proven.

Is there a real safety limit to worry about?

Yes, particularly with vitamin B6. PMS studies commonly used doses up to 100 mg a day, but that's already far above the European Food Safety Authority's conservative upper limit of 12 mg/day for adults. Documented case reports show sensory neuropathy — tingling, numbness, and in some cases an inability to walk — in people who took 2 to 6 grams of B6 daily for months, and there's at least one case of toxicity symptoms from long-term use of a multivitamin containing just 6 mg. The practical takeaway: 100 mg/day is the reasonable self-directed ceiling, not a floor to build up from.

Water retention isn't always benign, either. Persistent or sudden swelling — especially with shortness of breath, chest pain, or swelling in only one leg — can signal a heart, kidney, or liver problem that a supplement won't fix and may delay diagnosing. If swelling doesn't improve with the basics (less sodium, more movement, adequate hydration) within a week or two, that's a reason to see a doctor, not to add another supplement.

Frequently asked questions

Can I take magnesium and vitamin B6 together for bloating?
Both are commonly combined in PMS-focused formulas and one 2016 study found B6 may work even better paired with calcium — there's no published conflict between magnesium and B6 specifically, but stick to the studied dose ranges for each.

Is dandelion extract safe to take every day?
Short-term folk use suggests it's generally well tolerated, but because it hasn't been through large modern safety trials, treat it as a short-term option rather than an indefinite daily supplement, and stop if you notice digestive upset.

When is water retention a sign of something serious?
If swelling is sudden, one-sided, or comes with shortness of breath or chest pain, or if it doesn't improve after a week or two of basic changes, see a doctor — those are patterns a diuretic supplement can mask rather than fix.