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Dehydration

Last updated: March 2026

Last full review: February 2022

Next review date: March 2027

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Crohn's Colitis Symptoms

Living with Crohn’s or Colitis can sometimes mean that it's difficult to stay well hydrated. You may often have watery diarrhoea, or you may not feel like drinking because you’re fatigued, in pain or feel sick. But being dehydrated may make you feel worse and can be very serious.

This information is for anyone affected by Crohn’s or Colitis who would like to find out more about dehydration. Our information can help you:

  • Watch out for the signs of being dehydrated
  • Know the steps you need to take to stay hydrated
  • Understand what to do if you become dehydrated 

This information might use words you have not heard before. Our page on medical words can help provide an explanation.

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    • Mild or moderate dehydration can usually be treated quickly. But it can become severe if it is not treated. Severe dehydration needs urgent treatment or it can lead to complications.
    • Early signs of being dehydrated can include feeling thirsty and having dark yellow pee.
    • You may be more likely to become dehydrated if you often have watery diarrhoea, have had your colon removed, have a stoma or short bowel syndrome.
    • If you have symptoms of dehydration, drink plenty of fluids. This could be water or diluted squash. Keep drinking small amounts of fluids regularly.
    • If you have a high output stoma or short bowel syndrome, speak to your GP or IBD team to find out what type of rehydration would work best for you.

  • Your body needs the right amount of water and minerals to work properly. Your body loses fluids during the day through: 

    • Sweat
    • Tears
    • Moisture in your breath
    • Pee 
    • Poo 

    Usually, the fluid and salt from what you eat and drink make up for this loss. But you can become dehydrated if you lose more fluid than you take in. This can happen if you do not drink enough, or if you lose too much body fluid through: 

    • Sweating
    • Being sick
    • Diarrhoea

    Being dehydrated can cause you to weigh less. This is because there is less water in your body. Dehydration can be described as mild, moderate or severe depending on how much of your body weight has been lost through fluids.

    Mild or moderate dehydration can usually be treated quickly. If you are not treated, you can become severely dehydrated. Severe dehydration needs urgent treatment. Without urgent treatment, you can develop complications. This can include kidney problems or low blood pressure.

  • Early signs of being dehydrated can include: 

    • Feeling thirsty
    • Dark yellow pee. 

    Other symptoms include:

    • Not peeing as much as usual
    • Strong smelling pee
    • Feeling dizzy
    • Feeling tired
    • Dry or cracked lips, tongue and mouth

    Contact your GP or call 111 if you think you have severe dehydration. 111 can also be accessed online.

    Signs of severe dehydration include:

    • Being very thirsty
    • A very dry mouth
    • Fast breathing and fast heart rate
    • Feeling confused, tired or drowsy
    • Feeling dizzy when you stand up, and the feeling does not go away

  • Dehydration may not be a problem for everyone with Crohn’s or Colitis. However, you may be more likely to become dehydrated if you:

    • Often have watery diarrhoea.
    • Are being sick, or vomiting, repeatedly.
    • Have had your colon removed or have had ileal pouch-anal anastomosis (IPAA) surgery. This is also known as J-pouch surgery.
    • Have a stoma, also known as an ileostomy.
    • Have short bowel syndrome. Short bowel syndrome happens when the bowel does not have enough surface area to absorb nutrients from your food and drink. This can happen if you have had surgery to remove large sections of your small bowel.
    • Have bile salt malabsorption. This is a condition that causes more bile than 
      normal to be released from the gall bladder into the colon. This can cause watery diarrhoea.
    • Are sweating a lot. This might be during hot weather or exercise, or because you have a fever.
    • Are peeing more than usual. This can happen if you have uncontrolled diabetes, are drinking too much caffeine, or are taking diuretic medicines. Diuretic medicines are sometimes called ‘water tablets’, and these can make you pee more.
    • Have drunk too much alcohol.
    • Are being sick or have diarrhoea because of a stomach bug, bowel infection or food poisoning.

  • If you have symptoms of dehydration, drink plenty of fluids. This could be water or diluted squash. Keep drinking small amounts of fluids regularly. Avoid caffeine or alcohol as they can make dehydration worse.

    Replacing salts and sugars

    If you have been sick or have diarrhoea, you might need to increase the levels of salts and sugar in your body, as well as water. See the box below if you have a high-output stoma or short bowel syndrome.

    Oral rehydration solutions (ORS) are powders or tablets that are dissolved in water. They help the body replace water, salts and sugar. 

    You can buy oral rehydration solutions from most supermarkets and pharmacies. Your pharmacist can recommend a rehydration solution that is right for you. Your GP or IBD team might give you a recipe to make your own ORS at home. Make sure you follow all instructions carefully.

    If you have a high-output stoma or short bowel syndrome

    Speak to your GP or IBD team to find out what type of rehydration would work best for you. You are more likely to need more salt than most store-bought rehydration solutions provide. Your GP or IBD team may recommend drinking an oral rehydration solution with a higher salt level, also known as a sodium level.  

  • The easiest way to avoid dehydration is to make sure that you drink enough. The EatWell Guide recommends drinking six to eight glasses of fluids a day. Water and diluted squash are good choices to stay hydrated. When you are well hydrated, your pee should be a pale yellow colour.

    You may need to drink more when there is a higher risk of becoming dehydrated.

    This could be when:

    • The weather is very hot
    • You are sweating due to exercise
    • You have diarrhoea or are being sick

    Do not wait until you feel thirsty before you start drinking extra water. 

    Drinking more water than your body can process can make you very unwell or be dangerous. This can cause the amount of salt, or sodium, in your blood to become unusually low. Drinking too much fluid can make you: 

    • Feel sick
    • Be sick
    • Have a headache

    In rare cases, it can cause: 

    • Confusion
    • Fits
    • Coma 

    Drinking too many fluids can sometimes even cause death. If you think you have drunk too much, contact a healthcare professional.

  • If you have frequent diarrhoea, you may want to consider taking anti-diarrhoeal medicines. You should not take anti-diarrhoeal medicines if you are: 

    • In a flare-up. This is when your symptoms are worse or happen more often.
    • If you have a high temperature.
    • If you have blood in your poo.

    You may not be able to take anti-diarrhoeal medicines if you have a narrowing in your bowel called a stricture. You should check with your doctor or IBD team before taking anti-diarrhoeal medicines. 

  • If you have an ileostomy, food and drink pass through your small bowel, and waste comes out through an opening in your tummy called a stoma. Food and drink do not pass through your large bowel, which is where water and salts are usually absorbed. It is important to drink enough water to keep yourself well hydrated. Your IBD team may recommend that you add extra salt to your meals. This may be around a teaspoon a day.

    Oral rehydration solutions (ORS) can be useful if you have short bowel syndrome or a high-output ileostomy. Your IBD team will let you know the best ORS for you. It is important that you follow instructions carefully. You may need to avoid drinking plain water while you are having an ORS.

    If you have high or watery output from your stoma, your stoma nurse might recommend anti-diarrhoeal medicines, like loperamide. They may also recommend thickening sachets to put in your bag. This can help you manage your output.

    Read more about eating and drinking with an ileostomy in our life with a stoma information.

  • We follow strict processes to make sure our information is based on up-to-date evidence and easy to understand.

    Please email us at evidence@crohnsandcolitis.org.uk if:

    • You have any comments or suggestions for improvements
    • You would like more information about the sources of evidence we use
    • You would like details of any conflicts of interest

    You can also write to us at Crohn’s & Colitis UK, 1 Bishop Square, Hatfield, AL10 9NE, or contact us through our Helpline: 0300 222 5700

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