Þegar kemur að lyfjaskömmtun, treystir hún lyfjaróbótnum til að skammta lyfin.

In this sentence, Þegar kemur að ... is an idiomatic way to say when it comes to ... or as for ....

English uses a dummy subject: it comes to. Icelandic often does not need that extra subject in this expression, so Þegar kemur að lyfjaskömmtun is perfectly natural.

So even though the English translation has it, Icelandic can simply say:

• Þegar kemur að lyfjaskömmtun = When it comes to medication dosing

This is because Icelandic follows the V2 rule in main clauses: the finite verb normally comes in the second position.

If the sentence began directly with the subject, you would get:

• Hún treystir lyfjaróbótnum ... = She trusts the medication robot ...

But here the sentence begins with the introductory clause:

• Þegar kemur að lyfjaskömmtun, ...

Since that whole clause takes the first slot, the finite verb of the main clause comes next:

• Þegar kemur að lyfjaskömmtun, treystir hún ...

So this word order is normal and expected.

Here, að takes the dative case.

So grammatically, lyfjaskömmtun is dative here. The reason that may not be obvious is that this noun has the same form in several cases, so you do not see a visible ending change.

In other words:

• the case is dative
• the form just happens to stay lyfjaskömmtun

Because treysta takes a dative object when it means trust.

So:

• treysta einhverjum / einhverju = to trust someone / something

That means lyfjaróbótnum is in the dative singular definite form, meaning the medication robot.

The ending -num is a strong clue that you are looking at a dative definite form.

When treysta means to trust someone/something, yes, it normally takes the dative.

Examples:

• Ég treysti henni. = I trust her.
• Hann treystir kerfinu. = He trusts the system.

There is also a related expression:

• treysta á ... = to rely on / count on

That is a different construction with á and can have a slightly different feel from simple trust.

Til að + infinitive is a very common way to express to do something, often with a sense of purpose or intended function.

So here:

• til að skammta lyfin = to dispense the medicines

With treysta, this pattern means:

• treysta einhverjum til að gera eitthvað = trust someone to do something

So the sentence structure is:

• She trusts the robot
• to dispense the medicines

They come from the same root, but they are different parts of speech:

• skammta = a verb meaning to dose / dispense / portion out
• skömmtun = a noun meaning dosing / dosage / dispensing

So in this sentence:

• lyfjaskömmtun = medication dosing / medicine dispensing
• að skammta lyfin = to dispense the medicines

This is very common in Icelandic: a noun and a verb built from the same base.

In Icelandic compounds, the first noun often appears in a form based on the genitive plural stem.

So:

• lyf = medicine / drug
• lyfja- = the compound form used before another noun
• skömmtun = dosing / dispensing

Together:

• lyfjaskömmtun = medication dosing

This is a very common pattern in Icelandic compound words.

Lyfin is the definite plural form of lyf here, and in this sentence it is the direct object of skammta.

So:

• lyf = medicines / medicine (indefinite base form)
• lyfin = the medicines

Because it is a neuter noun, the nominative and accusative plural forms are the same, so the form lyfin does not visibly show the difference. In this sentence, it functions as the accusative object.

Using lyfin makes the noun definite: the medicines rather than just medicines.

Icelandic usually adds definiteness as an ending on the noun itself rather than using a separate word like the.

So:

• lyf = medicines / medicine
• lyfin = the medicines

In context, lyfin suggests specific medicines already known or understood from the situation.

Yes, it is natural here.

The opening part:

• Þegar kemur að lyfjaskömmtun

is an introductory clause, and Icelandic commonly separates that from the main clause with a comma:

• ..., treystir hún lyfjaróbótnum ...

So the comma helps mark the transition from the introductory phrase to the main statement, much like in English.

Yes. That would still be a complete and natural sentence:

• Hún treystir lyfjaróbótnum til að skammta lyfin.
• She trusts the medication robot to dispense the medicines.

Adding Þegar kemur að lyfjaskömmtun narrows the statement and means something like:

• When it comes to medication dosing, she trusts the medication robot to dispense the medicines.

So the first part adds context/focus, not basic grammatical completeness.