What supplements to take while fasting

Some supplements can disrupt fast, others can be taken during the fasting time. Supplements can also support fasting.
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Although intermittent fasting has many health benefits, supplementation may be necessary during this practice to ensure optimal intake of key nutrients. Some supplements may disrupt your fast, while others should not cause a problem at all. Key vitamins and minerals may best be taken during your eating window. 

Written by
Dr. Sara Diana Garduno Diaz
PhD & Senior Nutrition Consultant

When it comes to fasting, supplements seem to be a grey area of confusion. This is understandable, as in order to get the most out of intermittent fasting, we want to avoid eating or drinking anything that breaks the fast (1).

So, do supplements count? Mostly, breaking a fast refers to any calorie-containing foods or beverages, however, it can also include any supplements that trigger digestion or spike insulin levels. Hence, it is important to be mindful when supplementing during a fast because some supplements will indeed break your fast, kick you out of ketosis, and stop autophagy.

While other supplements won’t necessarily break your fast, they are not meant to be taken on an empty stomach. With all of this in mind, let’s have a look at some of the most commonly consumed supplements and how they might affect you while fasting.

Supplements that can work while fasting

B vitamins can be taken while fasting.
  • Creatine: Assuming this is a pure creatine supplement and not a sweetened mix, creatine is not likely to break your fast because it contains zero calories and does not affect your insulin levels. You should be ok taking it before or after a workout if you are training while fasting. 
  • Electrolytes: This usually refers to potassium, sodium, magnesium and calcium. As long as your electrolyte supplement doesn’t contain any sweeteners or calories, it is fine to take it during a fast. In fact, electrolytes may even help you manage the side effects of entering ketosis. They will also help you stay hydrated as electrolytes aid your body with retaining water. 
  • L-tyrosine: This supplement is meant to be taken on an empty stomach, so it is not a concern to take it when fasting. L-tyrosine can help you manage stress and support your mood. To be very clear, L-tyrosine is an amino acid, but since it is usually taken in such minimal dosages as supplement form, it is unlikely to break a fast.
  • Probiotics: These are beneficial gut bacteria. Certain types of probiotic supplements are meant to be taken without food, when stomach acid levels are lower. Others however work better when consumed as part of a meal. Thus, it is important to check the label on your probiotic supplement for the recommendations from the manufacturer. Most probiotics are calorie-free, so should not disrupt your fasting period.
  • Prebiotics: Not to be confused with the beneficial bacteria called probiotics, prebiotics refers to the fibre that feeds your good gut bacteria to support a healthy gut microbiome. If you are taking a pure prebiotic supplement, this will go in and out of your body without being digested, hence no calories will be absorbed and no insulin response will be triggered. However, if your prebiotic is a mix that includes other digestible carbohydrates you will need to be careful as it can affect your blood glucose levels and kick you out of your fasting zone. 
  • Water-soluble vitamins: Since vitamins B and C do not require fats to be absorbed, it is possible to take them just with water during a fasting period. Vitamin C is usually pretty mild on an empty stomach, however, vitamins from the B-complex can make some people feel nauseous when they’re consumed without food. You will need to check how B vitamin supplementation makes you feel, and then decide if your body can handle them on an empty belly or if you are better off taking them during your non-fasting period (2). 

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Supplements to save for your eating window

Omega-3 supplements break a fast.

Let’s now look at supplements that are best absorbed with food in your stomach (3). Apart from improved absorption, some other supplements will break your fast because of their effect on blood glucose levels or insulin, so it is best to save them for your eating window.

  • Amino acids: Two popular forms of amino acid supplements are L-glutamine and branched-chain amino acids (BCAAs). These are usually a no-go while fasting since they can kick you out of ketosis by raising your insulin levels. If you can plan your supplementation time, it is best to take these during your eating window (4).
  • Curcumin and omega-3 fatty acids: Supplements containing these two popular components are easier for your body to absorb when they are taken with food as it helps with theor absorption. For this reason it is recommended that you have them during the hours you will be consuming food. 
  • Chromium and vanadium: At the other side of the blood glucose regulation spectrum, these minerals can drop your blood sugar levels too low if they are consumed while you are fasting. If your blood sugar levels dip too low, you run the risk of experiencing hypoglycemia, meaning low blood sugar levels. This in turn will lead to a crash on your energy levels. Even a small bout of hypoglycemia can lead to challenges adjusting and managing your mood, so it is best to take them with food to avoid these unwanted side effects.
  • Fat-soluble vitamins: This category includes vitamins A, D, E and K, as well as multivitamins that contain fat-soluble ingredients. These vitamins do not absorb with water, so it is necessary to take them with a meal. If you are not sure, check the directions on the label. 
  • Gummy vitamins: These vitamins tend to be sweetened and made with gelatin, which is a form of protein. These components will break your fast since they are providing calories.
  • Iodine: For maximum absorption, it is best to take your iodide supplements with food.
  • Magnesium: Some people can experience an upset stomach when they take a magnesium supplement on an empty stomach. While it is not fully understood why, it likely has to do with muscle contraction. In general it is recommended that magnesium supplements be consumed along with food. 
  • Protein powder: Whether you are taking whey, collagen, or other forms of protein, any protein powder breaks your fast because it contains calories and triggers the insulin response in your body. 

Final thoughts

Some people can’t stomach any supplements at all without food. If that is your case, you can aim to consume your supplements around 20-30 minutes before you have a meal. This will respect your fast but not leave too much time for unwanted symptoms to show up (5).

If you take prescription medications, talk to your healthcare professional before you switch up your supplementation routine. Some medications have to be taken within specific time slots. For others, taking them on an empty stomach can interfere with their effects. 

Always remember that bodies respond differently, so observing how you react to specific supplements is important to find a schedule that works for you and your fasting model. 

Frequently asked questions

What supplements to take when fasting?

During fasting periods your body may be at risk of missing out on some key nutrients due to the limited intake of food. One possible way to make up for this is by taking dietary supplements. Some of the intermittent fasting supplements you might consider include vitamin D and omega 3 fatty acids as these are likely to be missing from your diet if you have not planned it carefully. 

What minerals to take while fasting?

In addition to the intermittent fasting supplements mentioned above, you might want to consider taking a magnesium supplement. This mineral helps regulate your muscle and nerve control as well as allowing you to experience less fatigue.

When should you take your vitamins when intermittent fasting?

Although the ideal time for supplementation depends on various factors, in general it is advised that intermittent fasting supplements be consumed during your eating window. 


  1. He, Sitian, et al. "Effect of vitamin D supplementation on fasting plasma glucose, insulin resistance and prevention of type 2 diabetes mellitus in non‑diabetics: A systematic review and meta‑analysis." Biomedical reports 8.5 (2018): 475-484.

  1. Czernichow, Sébastien, et al. "Antioxidant supplementation does not affect fasting plasma glucose in the Supplementation with Antioxidant Vitamins and Minerals (SU. VI. MAX) study in France: association with dietary intake and plasma concentrations–." The American journal of clinical nutrition84.2 (2006): 395-399.

  1. Xin, Wei, Wei Wei, and Xiaoying Li. "Effect of fish oil supplementation on fasting vascular endothelial function in humans: a meta-analysis of randomized controlled trials." PloS one 7.9 (2012): e46028.

  1. Jablecka, A., et al. "The effect of oral L-arginine supplementation on fasting glucose, HbA1c, nitric oxide and total antioxidant status in diabetic patients with atherosclerotic peripheral arterial disease of lower extremities." Eur Rev Med Pharmacol Sci 16.3 (2012): 342-50.

  1. Benzie, Iris, and J. J. Strain. "Effect of vitamin C supplementation on concentrations of vitamins C and E in fasting plasma." Asia Pacific journal of clinical nutrition 8.3 (1999): 207-210.

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