How to start fasting

Read the safety list first

Some people should not use an unsupervised eating window at all, including pregnancy, breastfeeding, anyone under 18, people who are underweight, anyone with a history of an eating disorder, and people on medicines that can drop blood sugar. The full list is Who should be careful with fasting.

A free timer cannot tell you that fasting is safe. If any of those groups or conditions might apply, talk to a clinician before you change when you eat. Feeling uncomfortable in the first week is not a reason to ignore that list.

If you feel dizzy, confused, faint, have chest pain, or feel as if you might pass out, stop the fast and eat. Those signs are not ordinary hunger. See When to stop a fast.

You already fast overnight

Most people already go ten to twelve hours between dinner and breakfast without calling it intermittent fasting. That overnight gap is a real start, and you do not need a new plan to notice it.

The pattern is a chosen stretch without calories. Water is almost always allowed, and black coffee and unsweetened tea are common. You do not need a detailed drink rule to begin: finish dinner, sleep, and wait on breakfast.

The hours count while you sleep. Do sleeping hours count toward a fast? compares that with the same hours spent awake.

Pick a first window you can live with

A calm first target is the overnight gap you already have, then twelve hours, then fourteen if work, sleep, and mood still feel ordinary. 16:8 can come later if a normal week still works. You do not have to get there.

Do not start with one meal a day, a 24-hour fast, or a public 72-hour challenge. Stay at the first step long enough to see a workday, a rest day, and a meal with other people. A window that feels easy once and then wrecks the next three days is not a start you can keep.

If you want more on when those eating hours sit in the day, Choosing a starting window covers morning versus evening. If you already mean a stretch past a day, start with Before a longer fast.

Water, coffee, and what you do not need

Drink water. Thirst often feels like hunger, especially in the morning. A mild pang that eases after a glass of water and leaving the kitchen is common, and hunger comes in waves. That kind of pang is not a reason to add extra fasting hours.

Black coffee is optional. It can take the edge off a caffeine headache for people who already drink it, and it can also make you shakier and more obsessed with the next meal. It does not make the fast healthier.

Apple cider vinegar, extra salt packets, teas sold as fat-burning, and sorting food into dirty versus clean do not make the first days easier. If the hours feel too hard, shorten the fasting stretch. You do not need to buy a product to start.

The first days

Tap End Fast when you eat so the history shows what you actually did. Ending earlier than you planned is still a finished fast. Do not delete that row, and do not start a longer fast the next day to make up for it.

A headache, a slump around 3 p.m., and a feeling that “nothing is happening” are common in the first week. Those are not a detox, and they are not a reason to ignore dizziness or other stop signs.

When the eating hours are open, eat enough: protein, vegetables and fruit, and enough total food that you are not starving by the next morning. Eating too little in those hours makes the next fasting stretch louder. This timer will not add a scale.

Too little sleep can make the same hours feel like a failure. Taking a rest day, or setting Custom to twelve hours, is part of starting, not a week that went wrong.

Using this timer

Open the online fasting timer and type twelve or fourteen hours in Custom for a first target. Use 16:8 when that still feels like a schedule you could live with on a normal week. Open counts elapsed time with no finish time, so the clock can match a plan you already have. It is not a reason to go longer than you meant to.

Start the timer when you stop taking calories by your rule. Tap End Fast when you eat, including when you eat early. Names such as Ketosis on the timer are stage names. They are not a reason to push through a first week that already feels unsafe.