Supplements for intermittent fasters

The intermittent fasting stack — split by timing

During the fast — what's tolerable

Water, black coffee, plain tea. Sodium chloride (a pinch of salt in water) prevents the "keto flu" / "fasting headache" that's mostly electrolyte-driven. Magnesium bisglycinate 200 mg in the early evening is fine and helps cramps. Creatine 3–5 g doesn't break the fast metabolically — it's not caloric in any meaningful sense and doesn't spike insulin; mix in plain water. The "does it break the fast" question has multiple answers depending on what you mean — for weight loss it's about calories; for autophagy nobody has good human data; for ketosis it's about glucose and protein. Pure water, salt, magnesium, and creatine are tolerated by every standard.

During the eating window — fat-soluble vitamins go with fat

Vitamin D3 + K2, omega-3 EPA/DHA, vitamin A, vitamin E — all absorb proportionally to the fat content of the meal. Take them with the largest fat-containing meal of the day. Iron supplementation is the opposite — take iron on a relatively empty stomach with vitamin C, then eat ≥1 hour later. Don't sandwich iron between calcium-rich foods.

Protein target in a compressed window

Hitting 1.4–1.8 g protein per kg of bodyweight in an 8-hour window requires intentionality. Whey or plant protein at 25–40 g per meal helps — for a 70 kg adult that's roughly 100–125 g daily across two or three meals. Inadequate protein on IF is the #1 reason for muscle loss in weight-loss-focused fasting.

Electrolytes — the underrated piece

Sodium losses are higher in IF than continuous eating because of lower glycogen (which binds water and sodium); the headaches, lightheadedness, and fatigue of the first 2–4 weeks are largely electrolyte-driven. Roughly 2–3 g sodium chloride/day extra during fasting hours; ORS-style salt sticks are convenient. Potassium from food (avocado, leafy greens, beans) in the eating window; supplemental potassium beyond food only with clinician guidance.

Creatine — the non-negotiable for trainers

For anyone doing resistance training while fasting, creatine 3–5 g daily is the most-evidence-backed supplement decision. Doesn't break the fast in any meaningful sense and provides the strength/lean-mass preservation that fasting alone doesn't.

Multivitamin coverage

If your eating window is genuinely 4–6 hours and varied food intake is hard to maintain, a low-dose daily multivitamin is reasonable insurance. Stick to RDA-range coverage; mega-dose multivitamins aren't needed.