Toàn cơ thể đang mệt.

Toàn cơ thể literally means the entire body or the whole body.

• toàn = whole, entire
• cơ thể = body

So the phrase points to the body as a whole, not just one part like the head, arms, or legs.

đang mệt means is tired, is feeling tired, or is currently tired.

• mệt = tired, fatigued, exhausted
• đang marks an ongoing or current state/action

So đang mệt suggests that the tiredness is happening right now.

Vietnamese often leaves out possessive words like my, your, or his/her when the meaning is clear from context.

So Toàn cơ thể đang mệt can naturally be understood as:

• My whole body is tired
• The whole body is tired

depending on the situation.

In English, you usually need my. In Vietnamese, it is often unnecessary if everyone already knows whose body is being talked about.

Here, mệt behaves like an adjective/state word meaning tired.

Vietnamese often uses adjectives directly as the predicate, without needing a verb like to be.

So:

• Toàn cơ thể đang mệt

works without any equivalent of English is.

A literal word-for-word structure is something like:

• whole body / currently / tired

This is very normal in Vietnamese grammar.

Because Vietnamese usually does not use a linking verb like English to be before adjectives.

Compare:

• English: The whole body is tired
• Vietnamese: Toàn cơ thể mệt

The adjective mệt can directly describe the subject.

Adding đang makes it more like is currently tired or is feeling tired right now.

Yes, the sentence can exist without đang.

• Toàn cơ thể mệt. = The whole body is tired.
• Toàn cơ thể đang mệt. = The whole body is tired right now / is currently feeling tired.

đang adds a sense of current, ongoing condition. With adjectives like mệt, it can make the feeling sound more immediate or temporary.

In everyday speech, people often omit đang unless they want to emphasize the present moment.

It is understandable and grammatical, but it sounds a bit formal, written, or slightly clinical.

In everyday speech, Vietnamese speakers are more likely to say things like:

• Cả người mệt. = My whole body feels tired.
• Cả người đang mệt.
• Toàn thân mệt mỏi.
• Người mệt quá. = I feel so tired.

So your sentence is not wrong, but it is less casual than some common alternatives.

They are similar, but the tone is a little different:

• toàn cơ thể = the entire body
  
  • more formal, neutral, sometimes medical or descriptive
• cả người = the whole body / all over
  
  • very common in everyday speech
• toàn thân = the whole body
  
  • also common, often used in health, medicine, or physical description

Examples:

• Cả người mệt rã rời. = My whole body feels exhausted.
• Đau toàn thân. = Full-body pain / pain all over the body.
• Kiểm tra toàn cơ thể. = whole-body examination

mệt usually means tired, fatigued, or exhausted, but depending on context it can also suggest:

• physically weak
• drained
• not feeling well
• worn out

For example:

• Tôi mệt. = I’m tired.
• Hôm nay thấy hơi mệt. = I feel a bit unwell/tired today.

So in your sentence, it could mean simple tiredness, but it may also imply that the body feels physically run-down.

In Vietnamese, words meaning whole/all/entire often come before the noun they modify.

So:

• toàn cơ thể = entire body
• toàn bộ ngôi nhà = the entire house
• toàn thân = whole body

This is normal Vietnamese word order.

Yes, you could, but the meaning changes slightly.

• Cơ thể đang mệt = The body is tired / The body is feeling tired
• Toàn cơ thể đang mệt = The whole body is tired

Adding toàn emphasizes that it is the whole body, not just one part.

That said, cơ thể đang mệt is a little unusual in casual conversation. Native speakers often prefer:

• Cả người đang mệt
• Toàn thân đang mệt
• Người đang mệt

depending on context.

You can add không before mệt:

• Toàn cơ thể không mệt. = The whole body is not tired.

If you want to keep đang, a natural pattern is:

• Toàn cơ thể không thấy mệt. = The whole body does not feel tired.
• Cả người không mệt. = I’m not tired all over / My whole body doesn’t feel tired.

In everyday Vietnamese, the version with cả người often sounds more natural.

A common way is to use có ... không:

• Toàn cơ thể có mệt không? = Is the whole body tired?

But in natural speech, people would more often say:

• Cả người có mệt không?
• Cả người mệt không?

Both mean something like Does your whole body feel tired?

A rough pronunciation guide is:

• Toàn ≈ twahn
• cơ thể ≈ kuh thay
• đang ≈ zang / yang (depending on accent)
• mệt ≈ met, but with Vietnamese tone

More importantly, pay attention to the tones:

• Toàn — huyền tone
• cơ — level tone
• thể — hỏi tone
• đang — level tone
• mệt — nặng tone

Tones matter a lot in Vietnamese, so hearing a native recording is very helpful.

Sometimes, but usually they would choose a more personal and natural everyday phrasing.

Instead of Toàn cơ thể đang mệt, a native speaker might say:

• Cả người tôi mệt quá. = My whole body feels so tired.
• Mình mệt khắp người. = I feel tired all over.
• Cả người đang rã rời. = My whole body feels worn out.
• Tôi thấy mệt toàn thân. = I feel tired all over my body.

So your sentence is fine for understanding grammar and meaning, but it is not the most conversational choice.