The short answer: the supplements most worth taking during a fast are sodium, potassium, and magnesium, ideally in a zero-calorie, zero-sweetener formula, because fasting makes you lose them faster than usual. Beyond minerals, a few other options have some support for making fasting easier, including L-theanine, ginger, and plain black coffee or tea. Anything with calories, amino acids, or added sweeteners (gummies, protein powders, BCAAs, sweetened electrolyte mixes) is where fasts most often get broken.

I coach people through fasting, and the same questions come up constantly: what should I take, what should I skip, and why do I feel terrible by hour 14? This guide answers all three, and it's honest about where the evidence is strong and where it's thin.

How to Tell if a Supplement Will Break Your Fast

I use three questions, the same ones from my complete list of what breaks a fast:

1. Does it contain calories?

2. Could it trigger a meaningful insulin response?

3. Does it work against the reason you're fasting?

Plain minerals pass all three. A gummy vitamin fails the first two, since most contain sugar. A sweetened powder with zero calories passes the first two but may fail the third if sweetness keeps your cravings going. Your own goal sets how strict to be: general weight loss and metabolic health leave more room, while autophagy or a strict clean fast calls for the simplest options.

The Supplements Worth Taking While Fasting

1. Electrolytes: sodium, potassium, and magnesium

This is the one category I'd put at the top for almost everyone. When you stop eating, insulin drops, and lower insulin tells your kidneys to release sodium instead of holding onto it. Water leaves with it, and potassium and magnesium shortfalls tend to follow. That's why the headache, dizziness, and fatigue that people blame on "hunger" are often electrolyte symptoms. I explain the mechanism in electrolytes for intermittent fasting and the symptom side in headaches while fasting.

What to look for: real milligram amounts of each mineral listed individually, zero calories, and no sugar. Be careful with sweeteners and "natural flavors," which I cover in the truth about stevia and fasting and what natural flavors really are. I compare the major brands in best electrolyte drinks for fasting.

2. Magnesium

Most adults already fall short of the recommended 310 to 420 milligrams a day, and fasting can widen the gap. Muscle cramps, poor sleep, and restlessness are common signs. A supplemental dose should stay under the NIH's upper limit of 350 milligrams a day, and the form matters if your stomach is sensitive, since some forms loosen stools. I wrote a full breakdown in magnesium for fasting.

3. L-theanine

L-theanine is an amino acid found in tea. A 2020 systematic review of nine studies found that 200 to 400 milligrams a day may help reduce stress and anxiety in people under stressful conditions, though the authors called for larger, longer trials. That makes it a reasonable option for the edgy, foggy stretch that shows up hours into a fast, but it isn't a proven fix, and the research isn't specific to fasting. Because it's an amino acid at a very small dose, it carries essentially no calories, though a strict fast purist may still want to weigh that for themselves.

4. Ginger

Ginger has the best evidence of this group for digestion. A systematic review of clinical trials found that divided daily doses of about 1,500 milligrams were useful for relieving nausea, while evidence for other digestive issues is limited. If you get queasy on an empty stomach or feel sluggish digestion when you break your fast, ginger is a sensible, food-based option.

5. Black coffee and plain tea

Not a supplement, but one of the most effective tools for hunger and focus during a fast. Coffee has almost no calories, and caffeine can blunt appetite. The line is what you add to it. I cover that in does coffee break a fast, and the full drink list is in what can I drink while fasting.

6. Ceylon cinnamon (a small role)

Cinnamon is often marketed for blood sugar, but the NIH's National Center for Complementary and Integrative Health says research doesn't clearly support using it for any health condition, partly because studies often don't specify which type was used. I treat it as a flavor with possible modest support, not a proven fasting aid. If you use it, Ceylon cinnamon is the one with only trace amounts of coumarin, a compound found in higher levels in cassia cinnamon that can matter for sensitive people over time.

Supplements to Take in Your Eating Window Instead

Fat-soluble vitamins (A, D, E, and K) absorb better with food, so they're better saved for meals. Iron and zinc can upset an empty stomach, so many people take them with food too. Plain creatine has no calories and is mostly relevant if you're training, but it doesn't have to be taken during your fast.

Supplements That Commonly Break a Fast

Gummy vitamins usually contain sugar. Protein powders, BCAAs, and essential amino acids contain calories and amino acids that most fasting standards treat as breaking a fast. MCT oil, butter, and other fats add calories. Sweetened electrolyte mixes range from a few calories to 50 or more, and many contain sweeteners that may keep cravings active. Capsules and tablets with coatings or binders are a gray area, especially for strict fasters.

How to Make Fasting Easier

Supplements are only part of it. These are the things I tell coaching clients:

Front-load your electrolytes. Many early-fast symptoms come from sodium loss, not willpower. Taking minerals in the morning, before the headache starts, is easier than chasing it.

Keep coffee and tea black. The fast is usually broken by what goes in them.

Skip the sweetness. If sweet flavors make you hungrier, a zero-sweetener electrolyte can make the fasted window easier to sit through.

Ease in. If you're new, start with a shorter window. My intermittent fasting for beginners guide covers how to build up.

Eat well in your window. Protein and whole foods at your meals make the next fast easier.

Where Optimize Fits

I built Optimize for exactly this situation: a single zero-calorie, zero-sugar, zero-sweetener formula that covers the supplements fasting calls for most. Each serving has 290 milligrams of sodium, 145 milligrams of potassium, and 30 milligrams of magnesium, plus 150 milligrams of L-theanine, Ceylon cinnamon, ginger, lemon peel, and vanilla bean. There are no natural flavors, no flavor carrier, no sweeteners, and no anti-caking agents.

Here's how it compares on the numbers, based on the product labels at the time of writing:

Optimize is built to be used more than once through a fasting day, with a label you can fully read, no hidden ingredients, and nothing that raises the "does this break my fast" question. For deeper brand comparisons, see Liquid IV vs LMNT, Instant Hydration vs LMNT, and does LMNT have maltodextrin.

Frequently Asked Questions

What is the best supplement to take while fasting?

An electrolyte supplement with sodium, potassium, and magnesium, and no calories, sugar, or sweeteners. Fasting increases how much of these minerals you lose, so they're the supplement with the clearest reason to take them. Optimize is the one I formulated for this purpose.

Do supplements break a fast?

Plain minerals, black coffee, and plain tea generally don't. Gummies, protein, BCAAs, MCT oil, and sweetened powders often do, either from calories or from ingredients that work against your fasting goal.

Can I take vitamins while fasting?

Most plain, calorie-free vitamins don't add meaningful calories, but fat-soluble vitamins (A, D, E, K) absorb better with food, and some vitamins and minerals can upset an empty stomach. Saving them for your eating window is simpler.

Do electrolytes help with fasting headaches?

Often, yes. Headaches in the first days of a fast are commonly linked to sodium and fluid loss, and replacing sodium, potassium, and magnesium is the most direct fix. Not everyone responds the same way, and a headache that's severe or won't go away deserves a doctor's attention.

How do I make fasting easier?

Replace electrolytes early, keep coffee and tea black, skip sweeteners if they trigger cravings, start with a shorter window, and eat protein and whole foods in your eating window. Supplements help, but they work best alongside those habits.

Always check with your doctor before fasting or adding supplements if you're pregnant, take medication, or have a medical condition, especially one involving blood pressure, kidneys, or blood sugar.

Fuel your fast, feel your best.

Sources and Further Reading

Magnesium: Fact Sheet for Health Professionals, NIH Office of Dietary Supplements https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/

Potassium: Fact Sheet for Health Professionals, NIH Office of Dietary Supplements https://ods.od.nih.gov/factsheets/Potassium-HealthProfessional/

Cinnamon: Usefulness and Safety, NIH National Center for Complementary and Integrative Health https://www.nccih.nih.gov/health/cinnamon

The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review, Plant Foods for Human Nutrition https://link.springer.com/article/10.1007/s11130-019-00771-5

Ginger in Gastrointestinal Disorders: A Systematic Review of Clinical Trials, Food Science & Nutrition https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6341159/

Role of Insulin-Mediated Antinatriuresis in Sodium Homeostasis and Hypertension, Hypertension (American Heart Association) https://www.ahajournals.org/doi/10.1161/HYPERTENSIONAHA.118.11728

What Breaks a Fast: The Complete List, Fasted State Supplements https://getfastedstate.com/blogs/news/what-breaks-a-fast-complete-list