Without food (with water): about 6–12 days (Goodman et al. 1980). Without water (with food): about 10–16 days, but dehydration starts within a day. Without both: up to about 4 days (TheVetDesk). These are lab and vet ranges, not safe limits: a pet rat needs fresh food and water every day, and any rat without water needs urgent vet care.
A pet rat must have fresh food and water every day. The ranges on this page come from lab studies and vet estimates; they are not a safe limit. Any pet rat that has gone without water, or has stopped eating, needs urgent care from an exotic-animal vet.
How long can a rat live without food?
How long can a rat live without food? If it still has water, a rat can survive roughly about 6–12 days. The best evidence comes from a 1980 study of starving lab rats with water available: 8-week-old rats survived 6–7 days and 16-week-old rats 11–12 days, while rats made obese survived 25–30 days (Goodman et al. 1980). Young rats run out of reserves fastest, because they have little fat and are still growing.
So how many days can a rat live without food, and how long does a rat live without food in practice? About a week for a young adult, up to about 12 days for a lean adult, and longer for a fat one. But survival isn't the same as being safe. Lab animal rules treat more than 12 hours without food as significant distress (Wayne State University IACUC), and a starving rat breaks down muscle and organ tissue long before it dies. How long rats live without food also depends on temperature, health and age, which is why every figure here is a range, never an exact day.
How long can pet rats go without food?
For a pet, the answer is: not even a full day if you can help it. Rats eat mostly at night in many small meals. A pet rat that hasn't eaten for 24 hours is either ill or has no access to food, and both need action now — refill, check the rat eats, and call an exotic-animal vet if it doesn't. PetMD notes that weight loss is the most common first sign of illness in pet rats.
How long can a rat live without water?
Water matters more than food. How long can a rat live without water while it still has food? In one study reported by the vet-reviewed site TheVetDesk, 16 rats given food but no water survived 10–16 days, 13 on average. We couldn't access the original study, so treat it as a rough guide. Rats eat less when they can't drink, which helps them hold on to water, but they are dehydrating the whole time.
How long can a rat go without water before it's in danger? Much less than that. Lab rules list more than 12 hours without water as significant distress, and signs of dehydration — sunken eyes, slow skin "tenting" and a tacky mouth — show up early (Montana State University IACUC). A rat on dry pellets with a jammed or empty bottle can be in trouble within a day. That's why the RSPCA Australia suggests two water bottles, in case one fails.
Signs of dehydration in rats
- sunken, dull eyes;
- skin that stays "tented" when gently lifted on the back;
- a tacky or dry mouth, and dry, small or missing droppings;
- lethargy, hunching and not eating;
- red-brown (porphyrin) staining around the eyes and nose, which often appears in stressed or ill rats (Montana State University IACUC).
Any of these needs an exotic-animal vet the same day. Offer water straight away, but don't force fluids into the mouth — your vet will decide how to rehydrate safely.
How long can a rat survive without food and water?
How long can a rat survive without food and water? Much less time than without either one alone. TheVetDesk (vet-reviewed) says rats can survive without both "for up to 4 days in most instances" and stresses that this should never be tested on a pet. So how long can a rat live without food and water? Up to about four days at most, with young, small, old or sick rats at much greater risk.
| Situation | Survival range | Source |
|---|---|---|
| No food, water available | about 6–12 days | Goodman et al. 1980: 6–7 days at 8 weeks old, 11–12 days at 16 weeks; fat rats 25–30 days |
| No water, food available | about 10–16 days | A study of 16 rats (average 13 days), reported by TheVetDesk; original not accessible |
| No food and no water | up to about 4 days | TheVetDesk (vet-reviewed) |
These figures describe survival in experiments and vet estimates, not how long a rat can safely be left. In the calculator, any pet scenario beyond 24 hours is flagged "Urgent — see a vet now".
How much food and water does a rat need each day?
How much do rats eat a day? An adult rat eats about 5 g of food per 100 g of body weight a day, and how much water does a rat drink a day? About 8–10 ml per 100 g (Wayne State University IACUC). For a typical 400 g pet that's about 20 g of food and 32–40 ml of water — a few tablespoons.
| Rat | Food a day | Water a day |
|---|---|---|
| 300 g (small doe) | about 15 g | about 24–30 ml |
| 400 g (typical adult) | about 20 g | about 32–40 ml |
| 500 g (big buck) | about 25 g | about 40–50 ml |
| Wild Norway rat on dry food | about 110 kcal a day (ICWDM) | ½–1 oz (15–30 ml) (ICWDM) |
Wild Norway rats on dry food need about ½–1 oz (15–30 ml) of water a day and less when they eat moist food (ICWDM). Rodents do much of their eating at night (Wayne State University IACUC), so food and water must be available around the clock. Feed a complete rat food rather than rabbit or hamster mix (RSPCA), and give fresh water every day.
Leaving a pet rat alone: how long is safe?
Can I leave my rat alone for a weekend? Only with someone checking in. Rats need fresh water every day and their bottles can leak or jam, so the safest plan is a sitter who visits at least once a day. A single overnight trip is usually fine if you leave plenty of food, two working water bottles and a cool, safe room.
Use this planning checklist before you go away:
- Two water bottles, both tested and full (RSPCA Australia suggests two in case one fails).
- Enough complete rat food for the whole time away plus a spare day, in a heavy bowl that can't tip.
- A daily visitor who knows your rats, checks water flow, refills food, spot-cleans and counts noses.
- Steady temperature: Merck gives 18–26 °C (64–79 °F); keep the cage out of sun and draughts.
- Your exotic vet's number and an emergency vet's details written down for the sitter.
- Watch-list for the sitter: not eating, hunched posture, laboured breathing, sunken eyes or red staining around the eyes — call the vet.
Can I leave my pet rat alone for 3 days? Not without a sitter. Even if food lasts, a single blocked bottle could leave your rats without water for most of that time. Rats are social, too: kept in pairs or groups (NFRS), they cope better with your absence than a lone rat, but company doesn't replace daily checks.
Will rats leave a house if there's no food?
Homeowners often hope that taking away food will make rats move out. Removing food helps, but on its own it rarely makes rats leave quickly. Here's why, from university pest-management sources:
- They forage widely. A Norway rat ranges over an area about 100–150 ft across each day and seldom goes more than 400 ft from its burrow; roof rats travel 100–300 ft for food (ICWDM). A rat in your walls may be eating in a neighbour's garden, a bird feeder or a bin.
- They eat almost anything. Norway rats eat grains, meat, fish, nuts, fruit and insects (ICWDM); roof rats eat fruit, nuts, plants, pet food and livestock feed.
- Water is often the limit. Norway rats need to drink standing water daily (Cornell IPM), but leaks, condensation and moist food can supply it.
- They can survive gaps. As above, a rat with water can live about a week or more without food, which is long enough to find a new source.
Can rats survive in walls without food? Only for days, not indefinitely — but rats in walls usually leave to feed and come back. University extension guides describe lasting control as three parts together: sanitation (removing food, water and shelter), rodent-proofing entry points, and population reduction by a professional where needed. For a problem in your home, contact a licensed pest professional or your local council.
Rat vs mouse without food
| Rat | Mouse | |
|---|---|---|
| No food (water available) | about 6–12 days | about 2–5 days |
| No water (food available) | about 10–16 days | serious dehydration within 1–2 days on dry food |
| Food eaten per 100 g body weight a day | about 5 g | about 12 g |
Mice have much faster metabolisms and less in reserve. See our guide to how long a mouse can live without food for the mouse figures.
How this rat survival calculator works
Choose the situation (no food, no water, or neither) and whether the rat is a pet or wild. The calculator shows the sourced survival range for that situation as a range in days — never a single number — plus how much food and water a rat needs each day. If you enter the hours or days since the rat last had food or water, it adds a status and a bar showing where that time sits against the range.
For pets, the status follows care thresholds, not survival limits: up to 12 hours "Within normal range — refill now"; 12–24 hours "Refill now and watch closely"; from 24 hours "Urgent — see a vet now"; and past the point where some rats died in studies, "Emergency". The 12-hour mark comes from lab animal welfare rules (Wayne State University IACUC). For wild rats, it simply says whether the time is within, near the end of or beyond the sourced range. Negative times show an error. The page gives facts, not instructions for harming animals.
Frequently asked questions
How many days can a rat live without food?
About 6–12 days if it has water: 8-week-old lab rats survived 6–7 days and 16-week-old rats 11–12 days (Goodman et al. 1980). Fat rats lasted longer.
How long can a rat go without water?
In one study reported by TheVetDesk, rats with food but no water survived 10–16 days (13 on average), but dehydration starts within a day. A pet without water needs a vet urgently.
How long can a rat live without food and water?
Up to about 4 days in most cases (TheVetDesk, vet-reviewed). Young, old or sick rats can die much sooner.
Can I leave my pet rat alone for 3 days?
Not without someone checking daily. Leave plenty of food and two working water bottles, and arrange a sitter who checks water flow every day.
Can I leave my rat alone for a weekend?
Only with a sitter visiting at least once a day. An overnight trip is usually fine with plenty of food and two tested water bottles.
How much does a rat eat a day?
About 5 g of food per 100 g of body weight (Wayne State University IACUC) — about 20 g for a 400 g rat.
How much water does a rat drink a day?
About 8–10 ml per 100 g of body weight — 32–40 ml for a 400 g rat. Wild Norway rats on dry food need ½–1 oz (ICWDM).
What are the signs of dehydration in rats?
Sunken eyes, skin that stays tented when lifted, a tacky mouth, few or dry droppings, lethargy and red staining around the eyes. See an exotic vet the same day.
Will rats leave if there is no food?
Rarely quickly. Rats forage 100–300 ft from the nest and can survive a week or more without food if they have water. Lasting control combines sanitation, sealing entry points and professional help.
Can rats survive in walls without food?
Only for days. Rats living in walls usually go out to feed and drink, then return.
How long can pet rats go without food?
For a pet, treat 24 hours without food as a reason to call a vet — healthy rats eat many small meals, mostly at night.
This calculator gives an estimate for education and fun. Every pet ages differently — for health decisions, talk to your veterinarian.