Can You Take Vitamins While Fasting?

Fasting can help you achieve weight loss objectives or general health goals, but it also has some gray areas. A question that frequently arises is whether vitamins will break your fast.  

To experience the benefits of fasting, you must avoid any food or drink that might break your fast. Yet because we’re eating less, we often need the help of vitamins and supplements to get the required nutrients. So can you take vitamins while fasting? 

Here’s what you need to know. 

Can You Take Vitamins While Fasting?

There’s no one-size-fits-all answer to this question, so you’ll have to do some research. Some vitamins break a fast, while others are perfectly fine to take during your fasting window. Other supplements even support fasting.

Another thing to consider is how long you’re fasting. The shorter your fast, the less likely you are to need vitamins. Supplementation only becomes critical when fasting longer than a week. But if you’re like most people and fasting for shorter intervals (intermittent fasting) and are reasonably healthy, vitamins are probably less of a concern. 

You should also think about your supplementation routine pre-fasting. Were you taking vitamins already? Do you eat a varied diet with a lot of healthy foods? If you weren’t already taking vitamins and your diet is adequate, you probably don’t have to worry about supplementation–unless your doctor recommends otherwise. 

The Two Categories of Vitamins

Vitamins fall into one of two categories. They are either fat-soluble or water-soluble. Whether or not you can take a vitamin without food depends on what category it falls into. 

  • Fat-soluble. Fat-soluble vitamins are stored in the liver and body fat, so you must eat them with foods containing fat. If you’re fasting, it’s likely your body won’t absorb them. Save your money and wait for your feeding window to take these vitamins. 
  • Water-soluble: Unlike fat-soluble vitamins, water-soluble vitamins leave your body during the day through liquids. Because they don’t get stored anywhere, you can take them while fasting. However, you may end up with an upset stomach. If you’re concerned about digestion, keep in mind that most people on short-term fasts don’t deplete enough water-soluble vitamins to adversely affect their health.

Supplements You Can Take While Fasting

Now let’s talk about supplements that are safe to take during your fast window. 


Electrolytes are substances that help the body regulate vital functions. These functions become depleted during physical activity, which is why certain collectives like high-endurance athletes take them. 

Fasting also depletes electrolytes. Taking the most common electrolytes–like magnesium, calcium, potassium, and sodium–is beneficial while fasting. They are excellent for hydration, as they support your body in retaining water. Plus, if you’re beginning the keto diet, electrolytes help with keto fog. 

The only word of caution is to make sure the supplement contains no calories or sweeteners. 


Gym-goers rejoice–creatine has zero calories and no effect on insulin levels, so it’s unlikely to break a fast. You can still reap the benefits of this supplement, so feel free to take it before or after your workout. 


While L-tyrosine is an amino acid (see the next section for reasons why amino acids should not be taken during your fasting window), it’s the exception to the rule. L-tyrosine is meant to be taken while fasting, and the dosage is so low that it shouldn’t break your fast. So if you take L-tyrosine for your mood or to assist with stress, you can keep doing so at any time of day. 


Probiotics are good gut bacteria, and there’s a lot of talk about them nowadays. If you want to supplement with probiotics, keep in mind that they’re not an automatic green light. Some are meant to be taken while fasting, while others aren’t. You’ll have to check the recommendations before proceeding.

However, most probiotic supplements are calorie-free. In this case, you won’t have to worry about disrupting your fast. 


Don’t confuse prebiotics with probiotics. Prebiotics refer to the food that good gut bacteria need to flourish. They’re fine to take when fasting, as pure prebiotic supplements essentially go right through your body. There is no digestion, you absorb no calories, and your insulin levels remain the same. 

However, it’s worth checking the label carefully before taking them. Some prebiotics are a mix of digestible carbs. These carbs may throw off your glucose levels and end your fast.  

Water-soluble Vitamins

Lastly, vitamins B and C are fine to take while fasting. As mentioned, the body absorbs them without fats from food, so taking them during a fast isn’t a waste of money. 

But just because you can take water-soluble vitamins without food doesn’t mean you should. Some people tolerate water-soluble vitamins better with food. Vitamin C is typically okay, but B vitamins may cause nausea. 

It’s a good idea to experiment with B vitamins first and see how your body responds to supplementation. It may be better to wait and take them with food. 

Supplements to Avoid While Fasting

Now let’s talk about the supplements that are best to leave for your eating window. Some absorb better when you’ve eaten, while others will break your fast altogether. 

Amino Acids

Some of the most popular amino acids are L-glutamine and branched-chain amino acids, also known as BCAAs. Fitness enthusiasts in particular want to know if amino acids are okay to take while fasting.

Unfortunately, it’s best to avoid them. Amino acids (except L-tyrosine) affect insulin levels, so save them for your eating window instead.  

Fat-soluble Vitamins

We talked above about how fat-soluble vitamins should be avoided during your fasting window. They don’t absorb with just a glass of water, so it’s essential to pair them with food. Several vitamins fall into this category: you’ll want to steer clear of vitamins A, D, E, and K while fasting. You should also be careful with multivitamins, as some have fat-soluble ingredients.  

Curcumin/Omega-3 Fatty Acids

Curcumin and omega-3 fatty acids are regularly combined in supplements, but it’s best to leave them for when you’re eating. These components absorb much better if you take them with a meal. 

Protein Powder

If you go to the gym during your fasting window, you’ll need to wait to take your protein powder. All protein powders contain calories, whether they’re whey, collagen, or a different form. They change your insulin levels and break you fast, so protein powder is strictly off-limits during your fasting window.  


If you want to avoid an upset stomach, save your magnesium supplement after your fast. More specifically, you should take the supplement alongside a meal. Experts have yet to fully understand the reasons why magnesium irritates an empty stomach, but muscle contraction is the likely culprit.  

Chromium & Vanadium

Most of the supplementation issues have to do with them raising your blood sugar levels too high. But the problem with chromium and vanadium is the opposite. Your blood sugar levels can get too low if you take these minerals while fasting. 

And anyone who’s experienced hypoglycemia knows how rough it can be. Your energy levels drop off sharply, causing you to crash. You’re also likely to experience difficulty regulating your mood. 

Unpleasant though these symptoms are, they’re easy to avoid. Simply wait and take chromium and vanadium with a meal. 


Plenty of people take gummy vitamins, and they may seem harmless. However, you should leave them for your eating window. Most gummies are manufactured with artificial sweeteners, and they also contain gelatin, which is a form of protein. Both the sweeteners and gelatin provide calories, and you already know that consuming calories breaks your fast. 


Finally, iodine supplements should be taken with food to allow it to absorb properly. 

Frequently Asked Questions

Here are some of the most common questions regarding vitamins and fasting.

Can you mitigate the effects of taking supplements on an empty stomach?

Does taking supplements on an empty stomach bother you? If you need to supplement but have to fast, try taking them about twenty to thirty minutes before you eat. You’ll stick to your fast, but this short time should prevent adverse side effects from popping up. 

What breaks a fast?

Any amount of calories technically breaks a fast. However, there is some debate about whether tiny amounts (like two to five calories in a cup of coffee) offset the benefits of autophagy. Some purists argue that water is the only thing you can consume while fasting. But if you drink your coffee black with no sugar, you’re unlikely to break your fast. 

What about prescription medications?

It’s always best to consult your provider before making changes to your supplementation regimen. Some prescription medicines must be taken at certain times. Others require you to take them with a meal to avoid unwanted effects. 

Final Thoughts

There are no hard-and-fast rules when it comes to supplementation while fasting. Some vitamins are fine, while others should only be taken while you’re eating. If you experience an upset stomach, it may be best to take supplements with food.