Why is the reheating temperature higher than the cooking temperature?

Because of what happens between cooking and reheating. When a cooked TCS food is cooled and stored, it can allow bacterial survival and regrowth, so reheating for hot holding must reach a temperature high enough to rapidly kill those pathogens — 165°F. A freshly cooked food goes onto the line at its cooking temperature, but a food that was cooked, cooled, and stored must be brought all the way to 165°F before it can be hot held again.

Do I have to reheat commercially processed food to 165°F?

No. Under §3-403.11, food taken directly from a commercially processed, hermetically sealed or intact package — such as canned soup or factory-sealed sauce — and reheated for hot holding only needs to reach 135°F. It was cooked and packaged under controlled conditions and has not been cooled and stored in the kitchen, so it carries less regrowth risk. Once that product is opened, cooled, and stored like house-prepared food, the 165°F rule applies again.

What are the rules for reheating in a microwave?

Food reheated in a microwave for hot holding must reach at least 165°F, be covered, be rotated or stirred partway through to reduce cold spots, and then stand covered for at least 2 minutes after reheating so the heat equalizes. The 2-minute stand time is essential and frequently skipped — microwaves heat unevenly, and the post-heating equalization is what eliminates the cold spots where bacteria could survive.

Can I reheat food in a steam table or warmer?

No. Hot-holding equipment like steam tables, heat lamps, and warmers is designed to maintain the temperature of already-hot food, not to raise the temperature of cold or cool food. It heats too slowly to move food through the danger zone within the required 2 hours. Reheat the food rapidly to 165°F on a stove, in an oven, or in a microwave first, and only then transfer it to hot-holding equipment set at 135°F or above.

How long can reheating take?

The food must reach 165°F within 2 hours of starting to reheat, and the reheating must be done rapidly. The 2-hour limit is a hard ceiling because reheating takes the food back through the temperature danger zone, where bacteria multiply. If the food has not reached 165°F within 2 hours, it has spent too long in the danger zone and must be discarded rather than served or held.

Reheating TCS Foods for Hot Holding: 165°F Rule

TL;DR

Reheating a time/temperature control for safety (TCS) food that was cooked, cooled, and is now going back into HOT HOLDING is governed by FDA Food Code §3-403.11, and it has one number that matters most: 165°F (74°C) for 15 SECONDS, reached rapidly and WITHIN 2 HOURS. This is higher than the 135°F hot-holding temperature and higher than most original cooking temperatures, because reheating has to kill any bacteria that grew back while the food was cooled and stored. The 2-hour limit is a hard ceiling on how long the food can take to climb through the temperature danger zone during reheating. Three points complete the rule. First, COMMERCIALLY PROCESSED, ready-to-eat food taken directly from an intact, hermetically sealed package and reheated for hot holding only needs to reach 135°F — because it was already processed for safety and has not been exposed to contamination the way house-cooked, cooled food has. Second, when reheating in a MICROWAVE, the food must reach 165°F, be covered, be rotated or stirred partway through, and STAND covered for at least 2 minutes after heating so the temperature equalizes. Third, hot-holding equipment such as steam tables and warmers may NOT be used to reheat — they raise temperature too slowly to clear the danger zone within 2 hours, and are only for maintaining already-hot food. The rule applies to reheating for HOT HOLDING; food reheated for immediate service to a customer is treated differently.

Why reheating has its own high temperature

It surprises new food handlers that reheating requires a HIGHER temperature than hot holding. Hot holding keeps food safe at 135°F or above, and many foods are originally cooked to temperatures well below 165°F. So why must reheated food hit 165°F?

The answer is what happened to the food between cooking and reheating. When a cooked TCS food is COOLED and STORED, it passes through and sits near the temperature danger zone, and even properly cooled food can allow some bacterial survival and regrowth. Reheating for hot holding is the step that has to undo that risk, so the Food Code sets a temperature high enough to rapidly destroy pathogens that may have grown back. A freshly cooked food goes onto the line at its cooking temperature; a food that was cooked yesterday, cooled, and stored has to be brought all the way up to 165°F before it can be hot held. For the danger-zone concept this rule is built around, see our guide to the temperature danger zone.

The core rule: 165°F for 15 seconds within 2 hours

Under §3-403.11, a TCS food that is COOKED AND COOLED on the premises and then reheated for hot holding must be reheated so that all parts of the food reach a temperature of at least 165°F (74°C) for 15 SECONDS. The reheating must be done RAPIDLY, and the 165°F must be reached WITHIN 2 HOURS of beginning the process.

Each element carries weight:

165°F for 15 seconds. The temperature must be measured at the thickest part or the center of the food, not at the surface, and it must hold for 15 seconds. Checking the temperature with a calibrated thermometer in the right spot is what separates compliance from a guess.

Rapidly, within 2 hours. The reheat has to move the food through the danger zone quickly. The 2-hour clock is the outer limit; if the food has not reached 165°F within 2 hours, it has spent too long in the danger zone and must be discarded rather than served.

The reason the 2-hour ceiling exists is that reheating necessarily takes the food back through the danger zone, and time in that zone is what lets bacteria multiply. A fast reheat minimizes that exposure; a slow one recreates exactly the risk the rule is meant to prevent. For how time itself can be managed as a control, see our guide to time as a public health control.

The commercially processed exception: 135°F

Not everything reheated for hot holding must reach 165°F. Under §3-403.11, food taken directly from a COMMERCIALLY PROCESSED, hermetically sealed container, or from an intact package from a food processing plant, and then reheated for hot holding, need only be reheated to 135°F (57°C).

The logic is about exposure. Commercially processed, ready-to-eat food — canned soup, factory-sealed sauces, and similar products — was already cooked and packaged under controlled conditions and has not been opened, cooled in a kitchen, and stored the way house-prepared food has. It carries far less risk of the bacterial regrowth that the 165°F standard is designed to kill, so the Code allows it to be brought up only to the hot-holding temperature of 135°F. The moment that product is opened and treated like house-prepared food — cooled and stored for later — the ordinary 165°F reheating rule applies again.

Food being reheated for hot holding	Required reheat temperature
TCS food cooked and cooled on premises	165°F for 15 seconds, within 2 hours
Commercially processed, sealed, ready-to-eat food	135°F
Any food reheated in a microwave	165°F + covered + rotated/stirred + 2-minute stand

Microwave reheating

Reheating in a MICROWAVE OVEN has extra requirements because microwaves heat unevenly, leaving cold spots where bacteria can survive. Under §3-403.11, food reheated in a microwave for hot holding must be rotated or stirred partway through, covered to retain moisture and promote even heating, heated so all parts reach at least 165°F, and then allowed to STAND COVERED for at least 2 MINUTES after reheating.

The 2-minute stand time is the part most often forgotten. It exists because heat continues to equalize through the food after the microwave stops, and that post-heating equalization is what eliminates the cold spots the microwave left behind. Skipping the stand time can leave portions of the food below the safe temperature even though the average reading looked fine. For the related cooking-temperature rules that use the same thermometer discipline, see our guide to minimum cooking temperatures.

Why you cannot reheat in hot-holding equipment

A steam table, heat lamp, or warmer is designed to MAINTAIN the temperature of food that is already hot — not to raise the temperature of food that is cold or cool. Using such equipment to reheat is a common and dangerous mistake, because these devices heat too slowly to move food through the danger zone within the required 2 hours.

The correct sequence is to reheat the food rapidly to 165°F using appropriate equipment — a stove, oven, or microwave — and only THEN transfer it to the steam table or warmer for hot holding at 135°F or above. Putting cold leftover soup directly into a steam table lets it sit for hours in the danger zone while it slowly warms, which is precisely the condition that grows pathogens. The equipment's job begins only after the food has already reached 165°F. For the cooling step that precedes any reheating, see our guide to two-stage cooling of TCS foods.

Frequently Asked Questions

What temperature must reheated food reach for hot holding?: Under FDA Food Code §3-403.11, a TCS food that was cooked and cooled on the premises and is being reheated for hot holding must reach at least 165°F (74°C) for 15 seconds, reheated rapidly and within 2 hours. This is higher than the 135°F hot-holding temperature because reheating must destroy any bacteria that grew back while the food was cooled and stored. The temperature is measured at the center or thickest part of the food with a calibrated thermometer.
Why is the reheating temperature higher than the cooking temperature?: Because of what happens between cooking and reheating. When a cooked TCS food is cooled and stored, it can allow bacterial survival and regrowth, so reheating for hot holding must reach a temperature high enough to rapidly kill those pathogens — 165°F. A freshly cooked food goes onto the line at its cooking temperature, but a food that was cooked, cooled, and stored must be brought all the way to 165°F before it can be hot held again.
Do I have to reheat commercially processed food to 165°F?: No. Under §3-403.11, food taken directly from a commercially processed, hermetically sealed or intact package — such as canned soup or factory-sealed sauce — and reheated for hot holding only needs to reach 135°F. It was cooked and packaged under controlled conditions and has not been cooled and stored in the kitchen, so it carries less regrowth risk. Once that product is opened, cooled, and stored like house-prepared food, the 165°F rule applies again.
What are the rules for reheating in a microwave?: Food reheated in a microwave for hot holding must reach at least 165°F, be covered, be rotated or stirred partway through to reduce cold spots, and then stand covered for at least 2 minutes after reheating so the heat equalizes. The 2-minute stand time is essential and frequently skipped — microwaves heat unevenly, and the post-heating equalization is what eliminates the cold spots where bacteria could survive.
Can I reheat food in a steam table or warmer?: No. Hot-holding equipment like steam tables, heat lamps, and warmers is designed to maintain the temperature of already-hot food, not to raise the temperature of cold or cool food. It heats too slowly to move food through the danger zone within the required 2 hours. Reheat the food rapidly to 165°F on a stove, in an oven, or in a microwave first, and only then transfer it to hot-holding equipment set at 135°F or above.
How long can reheating take?: The food must reach 165°F within 2 hours of starting to reheat, and the reheating must be done rapidly. The 2-hour limit is a hard ceiling because reheating takes the food back through the temperature danger zone, where bacteria multiply. If the food has not reached 165°F within 2 hours, it has spent too long in the danger zone and must be discarded rather than served or held.

Bottom Line

FDA Food Code §3-403.11 governs reheating TCS food for HOT HOLDING, and the central rule is 165°F (74°C) for 15 SECONDS, reached RAPIDLY and WITHIN 2 HOURS, for food cooked and cooled on the premises. That temperature is higher than the 135°F hot-holding standard and higher than most cooking temperatures because reheating must destroy bacteria that regrew while the food was cooled and stored. COMMERCIALLY PROCESSED, ready-to-eat food from an intact sealed package needs only 135°F, since it has not been kitchen-cooled and stored — but once opened and treated like house-prepared food, the 165°F rule returns. MICROWAVE reheating adds requirements: reach 165°F, cover, rotate or stir, and stand covered at least 2 MINUTES so the heat equalizes and cold spots disappear. Hot-holding equipment like steam tables and warmers may NEVER be used to reheat, because they raise temperature too slowly to clear the danger zone within 2 hours; reheat rapidly with proper equipment first, then transfer to hot holding at 135°F or above. If food has not reached 165°F within 2 hours, discard it. For related topics, see our guides to the temperature danger zone, minimum cooking temperatures, and time as a public health control.

Source: FDA Food Code 2022 — §3-403.11 Reheating for Hot Holding · FDA Food Code §3-403.11 as adopted — Reheating (full text) · University of Minnesota Extension — Time and Temperature Control