Rennet in medicines

This resource on rennet is for the Muslim community (including patients, carers, parents and members of the public). Healthcare professionals may also find this resource useful when supporting people with gathering and understanding information about their medicine(s).

It highlights the issues of rennet use in medicines that you should be aware of. There is also a table to help you understand if rennet is halāl or harām, according to each of the four Sunni schools of thought.

Table Of Contents
  1. What is rennet?
  2. How rennet is used in medicines
  3. How the use of rennet in medicines affects the Muslim community
  4. Is rennet halāl or harām?
  5. Difference of opinions, minority views and exceptions
  6. Halāl alternatives and substitutes
  7. How do I find out if rennet has been used to make a medicine?
  8. Summary
  9. References and further reading

What is rennet?

Rennet is a complex mixture of enzymes. It is usually derived from the lining of the stomach of young animals like goats, lambs, calves (bovine), pigs (porcine) etc. 1

Rennet substitutes can be sourced from certain plants such as artichokes and nettles. 1 Alternatives can also be sourced from yeasts, fungi, or bacteria.2

A peaceful calf sleeps on hay, showcasing rural farm life and livestock tranquility.

How rennet is used in medicines

Bovine rennet is is an added enzyme traditionally used to extract lactose from cow’s milk. The lactose is then used as a filler and diluent powder and as an aid in the manufacturing of medicines.

Some manufacturers now use vegetarian processes to extract lactose from milk.3

How the use of rennet in medicines affects the Muslim community

The Muslim community needs to be aware that if rennet is used to extract lactose in the manufacturing of medicines, then it may be derived from animal sources, such as calves that were not Islamically slaughtered, or from other harām sources such as pigs. Some manufacturers now use vegetarian processes to extract lactose from milk. However, it is best to check the source and for halāl-certification to ensure halāl-compliant manufacturing. For further information on lactose, see our guide on Lactose use in medicines.

It is also important to note that information regarding cross-contamination with harām sources (e.g. pork and alcohol) is not always readily available from manufacturers.

It is important for the Muslim community to:

  1. Check if your medicine contains lactose and if rennet was used in the extraction process. If rennet was used, it is important to clarify its source
  2. Check for halāl-certification. 

To find out this information, see section on How do I find out if rennet has been used to make a medicine?. You may need to directly contact the manufacturer of your medicine to find out if rennet was used in the extraction process, the source of rennet and for halāl-certification (manufacturers may have limited information). This is because the product information only lists lactose and not rennet (as it is used as an enzyme in the manufacturing process). You can also speak to your local pharmacist for advice and support.

Is rennet halāl or harām?

The table below summarises the rulings of rennet according to the four Sunni schools4:

ḤanafīMālikīShāfiʿīḤanbalī
Majority view of rennet derived from animals that are Islamically slaughtered e.g. goats, lambs, calves (bovine)

✅
Legally pure (ṭāhir) and halāl to consume.		✅
Legally pure (ṭāhir) and halāl to consume.		✅
Legally pure (ṭāhir) and halāl to consume.		✅
Legally pure (ṭāhir) and halāl to consume.
Majority view of rennet derived from animals that are not Islamically slaughtered e.g. goats, lambs, calves (bovine)✅
Rennet from dead animals is considered legally pure (ṭāhir) and halāl to consume according to most, even if the animal was not Islamically slaughtered (permissive view).

Reasoning: Rennet is an enzyme and remains unaffected by the animal’s death. Classical scholar al-Jaṣṣāṣ stated that milk and rennet remain legally pure (ṭāhir) after an animal’s death.		✅
Rennet from dead animals is considered legally pure (ṭāhir) and halāl to consume (generally permissive view).

Reasoning: Rennet is extracted from the stomach lining, which is not directly affected by the death of the animal. It is not considered contaminated unless mixed with impurities.		❌
Rennet from dead animals is considered legally impure (najis) and harām (strict view).

Reasoning: The general rule is that dead animals are legally impure (najis), and rennet comes into direct contact with the impure stomach.		❌
Rennet from dead animals is considered legally impure (najis) and harām (strict view).

Reasoning: All parts of a dead animal are considered legally impure (najis) under general Islamic law. Rejects the argument that rennet is isolated from the carcass’s impurities.
Rennet substitute from porcine (pig)❌Harām ❌Harām ❌Harām ❌Harām
Rennet substitutes from plants, yeasts, fungi, or bacteria✅Halāl ✅Halāl ✅Halāl ✅Halāl

Difference of opinions, minority views and exceptions

There is a difference of opinions when rennet is derived from animals not Islamically slaughtered e.g. goats, lambs, calves (bovine).

Among Ḥanafīs Abu Yusuf & Muhammad: Liquid rennet may become legally impure (najis) if it comes into contact with the impure stomach lining. However, solid rennet remains legally pure (ṭāhir) and halāl to consume.

Minority view among Mālikīs: If contamination occurs, washing cannot purify it.

In summary, according to the four schools of thought, rennet from animals that have been Islamically slaughtered is legally pure (ṭāhir) and halāl, and rennet from pig is harām. The difference of opinion arises when rennet comes from dead animals (mayyitah) or animals not Islamically slaughtered.

Halāl alternatives and substitutes

If you are seeking halāl products, look for halāl-certified sources (where available and possible). Rennet alternatives can also be sourced from yeasts, fungi, or bacteria.

How do I find out if rennet has been used to make a medicine?


Rennet is an added enzyme used to extract lactose and is not usually listed as an ingredient or excipient in the product information. However, you would need to consider if rennet was used if you see lactose listed. You can check if a medicine contains lactose (rennet is an added enzyme used to extract lactose) using the relevant product patient information leaflet (PIL) or summary of product characteristics (SPC) available on the electronic medicines compendium (emc) website. However, you may need to contact the manufacturer to find out the source of rennet and for halāl-certification. You may also find our resource on ‘How to find out if a medicine contains harām ingredients or excipients’ useful. If you are still unsure if your medicine contains lactose or if rennet is used to extract lactose, speak to your local healthcare professional such as your local pharmacist. 

It is important to remember that even if a medicine contains a harām ingredient or excipient, it does not always mean it is prohibited to take. If you find out a medicine contains harām ingredients or excipients from harām sources, then see our guide on ‘What to do if a medicine contains harām ingredients or excipients’. The guide includes the conditions of when it is acceptable to take a medicine that contains harām ingredients or excipients from harām sources. It may also help you make informed decisions on the next steps in discussions with your healthcare professional. If you are still not sure if it is permissible to take your medicine, then speak to your local Imam or trusted Islamic scholar (ideally who has relevant knowledge and expertise in the Fiqh of medicines).

Please continue to take your medicine(s) as prescribed.
Do not stop taking your medicine(s), change your medicine(s), or change the way you take your medicine(s) without discussing this with the healthcare professional who prescribed it for you.

Summary

  • All four Sunni schools agree that rennet from animals that have been Islamically slaughtered is legally pure (ṭāhir) and halāl to consume
  • All four Sunni schools also agree that rennet from pig is harām
  • The difference of opinion arises when rennet comes from dead animals (mayyitah) or animals not Islamically slaughtered
  • You can check if a medicine you are taking contains lactose (rennet is used to extract lactose) using the PIL or SPC. If you are unsure, then speak to your local pharmacist
  • You can check if rennet was used to extract the lactose and its source with the manufacturers
  • You can also check if there is halāl-certification available for the medicine, to ensure halāl-compliant manufacturing (manufacturers may have limited information)
  • If you are unsure if your medicine is permissible to take, then speak to your local Imam or trusted Islamic scholar (ideally who has relevant knowledge and expertise in the Fiqh of medicines).

References and further reading

  1. Tharuka Gunathilake, Taiwo O. Akanbi, Quan Van Vuong, Christopher J. Scarlett, Colin J. Barrow,
    Chapter 4 – Enzyme technology in the production of flavors and food additives, Value-Addition in Food Products and Processing Through Enzyme Technology, Academic Press, 2022, Pages 45-55,
    Available from https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/rennet ↩︎
  2. Bruno Ricardo de Castro Leite Júnior, Fabiana de Oliveira Martins, Larissa Mattos Trevizano, Arthur Pompilio da Capela, Thainá de Melo Carlos Dias, Ana Flávia Coelho Pacheco, Eliane Mauricio Furtado Martins, Chapter 7 – Applications of enzymes in food processing, Research and Technological Advances in Food Science, Academic Press, 2022, Pages 175-194, Available from: https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/rennet ↩︎
  3. Why can’t all drugs be vegetarian? BMJ 2014;348:g401 Available at: https://www.bmj.com/bmj/section-pdf/752705?path=/bmj/348/7944/Analysis.full.pdf ↩︎
  4.  Ruling on rennet according to the four sunni schools of thought by Shaykh Dr Rafaqat Rashid  ↩︎
Scroll to Top