Learn Hardcore Malay: Saya mengukur suhu badan saya dan lihat ia naik sedikit apabila saya bimbang. - I measure my body temperature and see it rise a little when I am worried.

The base verb is ukur (to measure).
When you add the meN- prefix, you get mengukur, which is the normal active verb form in standard Malay.

mengukur suhu badan saya = I measure my body temperature
ukur suhu badan saya can appear in:
- commands: Ukur suhu badan saya. (Measure my body temperature.)
- informal speech where prefixes are often dropped

In a neutral, complete sentence with saya as the subject, mengukur is more standard and sounds more complete/formal than just ukur.

Why is it suhu badan saya and not suhu saya? Are other phrases possible?

suhu badan saya literally means my body temperature:

suhu = temperature
badan = body
saya = my / I

If you say suhu saya, it is understandable in context, but less precise; it could be interpreted as my temperature in a vague sense.

Other natural options:

suhu badan saya – very common and clear
suhu tubuh saya – also correct; tubuh is another word for body, slightly more formal/literary
suhu badan (without saya) – if it’s already clear you are talking about your own body, you might drop saya in casual contexts

For learners, suhu badan saya is a safe, natural choice.

Why is saya omitted in the second part (dan lihat ia naik sedikit)? Should it be dan saya lihat?

Yes, the full, explicit form would be:

Saya mengukur suhu badan saya dan saya lihat ia naik sedikit…

Malay often omits repeated subjects when they are clear from context, especially in speech and informal writing. So:

… dan lihat ia naik sedikit …
is understood as
… dan (saya) lihat ia naik sedikit …

Both are grammatically acceptable. For learners and in more formal writing, dan saya lihat is clearer and a bit more standard.

Why does the sentence use ia for it? Can I use dia or itu instead?

In this sentence, ia refers to suhu badan saya (my body temperature).

ia – a third-person pronoun, often used in more formal Malay, usually for things, animals, or as a neutral pronoun. Here it works like it.
dia – commonly used for people, and also for animals in everyday speech. Many speakers also use dia for things in casual conversation, but textbooks often say dia = he/she.
itu – usually a determiner/demonstrative meaning that, but in context can function like that/it.

In this sentence:

ia is the most textbook-like and neutral for temperature.
dia would sound a bit odd in formal writing, but might appear in casual spoken Malay.
itu could be used in a more deictic way (pointing):
- … dan lihat suhu itu naik sedikit … (… and see that temperature go up a bit …)

So ia is a good, safe choice here.

What exactly does naik sedikit mean? Is there a difference between naik and meningkat?

naik literally means to go up / to rise.
sedikit means a little / a bit.

So naik sedikit = go up a little / rise a bit.

meningkat also means to increase / to rise, often sounding slightly more formal or technical:

suhu badan saya meningkat sedikit – my body temperature increases a little (sounds a bit more formal/clinical)
suhu badan saya naik sedikit – my body temperature goes up a bit (more everyday/neutral)

In conversation or neutral writing, naik sedikit is very natural.

How do we know the tense here? Is this past, present, or a general habit?

Malay verbs usually do not change form for tense. mengukur, lihat, naik all stay the same whether the action is past, present, or future. The tense or aspect is understood from context or from time words.

This sentence by itself can mean:

I measure my body temperature and (I) see it go up a bit when I am worried.
→ a general habit or repeated pattern
I measured my body temperature and (I) saw it go up a bit when I was worried.
→ a specific event, if the context is clearly in the past

To make it explicitly past or habitual, you might add words like:

tadi (earlier), semalam (last night) for past
selalu (always), setiap kali (every time) for habitual

What is the difference between apabila, bila, and ketika? Could I replace apabila here?

In the sentence, apabila saya bimbang means when I am worried.

apabila – neutral and acceptable in both spoken and written Malay; slightly more formal than bila.
bila – very common in speech, can mean when or (informally) if. Often seen in casual writing.
ketika – can mean when / at the time (that); often used with nouns or clauses, and slightly more formal or literary.

Here you could say:

apabila saya bimbang – good, neutral-standard
bila saya bimbang – very natural in conversation, and fine in less formal writing
ketika saya bimbang – also correct; may sound a bit more formal or emotional/literary depending on context

All three work here; apabila is a safe textbook choice.

What is the difference between bimbang and risau? Both mean worried, right?

Yes, both bimbang and risau convey the idea of worry/anxiety.

bimbang – can sound a bit more general/formal; used in writing and speech.
- saya bimbang tentang kesihatan saya – I am worried about my health.
risau – very common in everyday spoken Malay; also used in writing but feels more colloquial in tone.
- saya risau tentang kesihatan saya

In this sentence, apabila saya bimbang could naturally be apabila saya risau, especially in speech. The core meaning is the same; the nuance is mainly register (formality and style).

Why is it suhu badan saya, with saya at the end, and not saya suhu badan or saya badan suhu?

In Malay noun phrases, the possessor comes after the thing possessed. The typical order is:

[thing] + [possessor]

So:

suhu badan saya → temperature
- body
  - my
    = my body temperature

You cannot say saya suhu badan for my body temperature; that order is wrong.

More examples of this pattern:

buku saya – my book
rumah mereka – their house
nama kawan saya – my friend’s name
warna mata dia – his/her eye color

So suhu badan saya follows the normal Malay noun phrase structure.

Could I use melihat instead of lihat? What is the difference?

Yes, you could use melihat, which is meN- + lihat, the active verb form:

dan (saya) melihat ia naik sedikit …

Differences:

lihat – base form; used in commands (Lihat sini! = Look here!), in some fixed expressions, and in more relaxed speech (often dropping prefixes).
melihat – more complete/formal verb form; common in standard written Malay.

In spoken Malay, people often say:

… dan saya nampak ia naik sikit … (… and I see/notice it go up a bit …)

For a neutral written style, dan saya melihat ia naik sedikit… is slightly more formal, while dan saya lihat ia naik sedikit… is acceptable and a bit simpler.

Is the overall sentence natural in Malay? How might a native speaker also say this?

The sentence is understandable and grammatically acceptable, especially in a more formal or textbook context. A native speaker might also phrase it in slightly different but equivalent ways, for example:

Saya mengukur suhu badan saya dan saya dapati ia naik sedikit apabila saya bimbang.
(I measure my body temperature and find that it goes up a bit when I am worried.)
More conversational style:
Bila saya bimbang, saya akan ukur suhu badan saya dan saya nampak ia naik sikit.
(When I’m worried, I’ll measure my body temperature and I see it go up a bit.)

Your original sentence is fine; these examples just show small style and register variations a native speaker might choose.