Short answer
No. In the Hanafi school injections into a muscle, a vein or under the skin, such as insulin, vaccines and antibiotics, do not break the fast, because they do not enter through an open passage. Most Hanafi muftis say the same of IV drips, but a nutritional drip taken just to ease the fast is disliked, and some scholars say it breaks the fast.
Injections do not break the fast, whether medical, dental or a vaccine. A saline or glucose drip also does not break it according to most Deobandi fatwa bodies, but taking a nourishing drip without medical need is makruh because it defeats the purpose of fasting. Enemas and suppositories are different: they enter an open passage and break the fast.
The four schools agree on this.
Explanation
The Hanafi jurists say a fast is broken when something reaches the inside of the body through a natural opening, such as the mouth, nose or back passage. A needle makes its own small opening into muscle or a vein and does not pass through such a passage. On this basis Maulana Ashraf Ali Thanawi and the later Hanafi muftis ruled that injections do not break the fast.
- Insulin, blood thinners and other regular injections: fast is valid.
- Vaccines, including flu and travel vaccines: fast is valid.
- A local anaesthetic at the dentist: fast is valid, but do not swallow the water or blood.
- Enemas and suppositories: the fast is broken, qada only.
IV drips. Most Hanafi fatwa bodies hold that a drip does not break the fast either, since it goes into a vein. Others, including the International Islamic Fiqh Academy, hold that nutritional drips and injections do break the fast because they replace food. In practice, anyone ill enough to need a drip is usually allowed not to fast anyway, so they can simply make the day up. Using a nutritional drip to avoid feeling hungry is not acceptable on any view.
Scholars of all four schools today broadly agree that ordinary injections do not break the fast; the difference is over drips that nourish the body. Medical cases vary, so ask a qualified mufti about treatments such as dialysis or chemotherapy. If your illness means you cannot fast at all, see can you skip fasting if you are sick.
Ask a mufti about your own case. This answer explains the general ruling. When the details of your situation matter, as they do here, ask a qualified mufti and give them the full facts. Where to ask a scholar.
The evidence
Quran, Surah Al-Baqara 2:187
أُحِلَّ لَكُمْ لَيْلَةَ ٱلصِّيَامِ ٱلرَّفَثُ إِلَىٰ نِسَآئِكُمْ ۚ هُنَّ لِبَاسٌۭ لَّكُمْ وَأَنتُمْ لِبَاسٌۭ لَّهُنَّ ۗ عَلِمَ ٱللَّهُ أَنَّكُمْ كُنتُمْ تَخْتَانُونَ أَنفُسَكُمْ فَتَابَ عَلَيْكُمْ وَعَفَا عَنكُمْ ۖ فَٱلْـَٰٔنَ بَٰشِرُوهُنَّ وَٱبْتَغُوا۟ مَا كَتَبَ ٱللَّهُ لَكُمْ ۚ وَكُلُوا۟ وَٱشْرَبُوا۟ حَتَّىٰ يَتَبَيَّنَ لَكُمُ ٱلْخَيْطُ ٱلْأَبْيَضُ مِنَ ٱلْخَيْطِ ٱلْأَسْوَدِ مِنَ ٱلْفَجْرِ ۖ ثُمَّ أَتِمُّوا۟ ٱلصِّيَامَ إِلَى ٱلَّيْلِ ۚ وَلَا تُبَٰشِرُوهُنَّ وَأَنتُمْ عَٰكِفُونَ فِى ٱلْمَسَٰجِدِ ۗ تِلْكَ حُدُودُ ٱللَّهِ فَلَا تَقْرَبُوهَا ۗ كَذَٰلِكَ يُبَيِّنُ ٱللَّهُ ءَايَٰتِهِۦ لِلنَّاسِ لَعَلَّهُمْ يَتَّقُونَ ﴿١٨٧﴾
It has been made permissible for you the night preceding fasting to go to your wives [for sexual relations]. They are clothing for you and you are clothing for them. Allah knows that you used to deceive yourselves, so He accepted your repentance and forgave you. So now, have relations with them and seek that which Allah has decreed for you. And eat and drink until the white thread of dawn becomes distinct to you from the black thread [of night]. Then complete the fast until the sunset. And do not have relations with them as long as you are staying for worship in the mosques. These are the limits [set by] Allah, so do not approach them. Thus does Allah make clear His ordinances to the people that they may become righteous.
The fast is about holding back from eating and drinking, which is why scholars ask whether a treatment is a form of taking in food through a passage.
Where the ruling is recorded
- Imdad al-Fatawa, Kitab al-Sawm. Injections do not break the fast because the medicine does not reach the inside through a natural passage.
- al-Hidaya, Kitab al-Sawm, chapter on what requires qada and kaffarah. An enema breaks the fast with qada only.
- Fatawa Mahmudiyya, Kitab al-Sawm. Injections, including into a vein, do not break the fast.
This answer is pending review by the scholars on our team. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.