Introduction Intermittent fasting (IF) is a dietary pattern used to improve metabolic health, body composition, and cognitive function. Reducing daily eating windows can alter nutrient intake and absorption, so many people ask whether supplements should be part of their IF plan and which ones support fasting physiology without undermining its benefits. Why consider supplements with IF? Fasting changes hormone levels, renal electrolyte handling, and nutrient exposure. Lower insulin and shifts in kidney function can increase sodium excretion and alter magnesium and potassium balance. Supplements are a practical way to address potential gaps—particularly for micronutrients that are hard to obtain in a compressed eating window—but their timing and formulation matter. Fast-safe versus fast-breaking supplements Supplements that are essentially non-caloric and do not induce an insulin response are generally considered fast-safe. These include many electrolytes (magnesium, potassium), certain minerals, and non-caloric herbal extracts. In contrast, protein powders, branched-chain amino acids (BCAAs), and caloric oils (MCT oil) provide energy and amino acids that will interrupt the fasted state and can blunt autophagy or ketone production. Evidence-based supplement choices for IF - Electrolytes: Magnesium, potassium, and sodium are commonly recommended to prevent headaches, cramps, and fatigue during adaptation. For practical guidance on electrolyte use, see Do you need electrolyte supplements? - Vitamin D and B12: Deficiencies are prevalent in many populations and can persist irrespective of eating patterns. Fat-soluble vitamin D is best taken with a meal containing fat to improve absorption. - Omega‑3 fatty acids (EPA/DHA): These support cognitive and cardiovascular health and do not disrupt fasting when taken with food in the eating window. - Adaptogens and targeted botanicals: Compounds such as rhodiola or green tea extract have some evidence for supporting energy and metabolic function; formulations without added sugars are preferred. Timing and formulation considerations Water-soluble vitamins and minerals can often be taken during a fast, but some people experience gastrointestinal discomfort when taking certain supplements on an empty stomach. Fat-soluble vitamins (A, D, E, K) should be taken with meals. Avoid flavored powders or liquid formulations that contain sugars or caloric additives during fasting windows. Choosing quality products Select supplements with transparent labeling, minimal fillers, and third-party testing when possible. For broader context on product selection and brand considerations, consult relevant selection resources such as brand selection guidance or general information available at TopVitamine. Practical summary Supplements can support intermittent fasting by addressing common nutrient shortfalls and easing adaptation symptoms, provided they are chosen and timed appropriately. Use non-caloric electrolytes and select water-soluble nutrients for the fasted period if tolerated, and reserve caloric or fat-dependent supplements for the eating window. For a focused review of supplementation strategies during fasting, see [Should I Take Supplements During Intermittent Fasting for Better Results](https://www.topvitamine.com/blogs/news/should-i-take-supplements-during-intermittent-fasting). Consultation with a healthcare professional is advised before starting new supplements, especially for people with medical conditions or those taking medications.