У мене болить підшлункова залоза.

Because this is a very common Ukrainian pattern for talking about pain, symptoms, and possession-like states.

• У мене literally means at me
• У мене болить ... is the normal way to say that some body part hurts

So Ukrainian often frames this as:

• At me hurts X

rather than:

• My X hurts

A very common pattern is:

• У мене болить голова = My head hurts
• У мене болить спина = My back hurts

This sounds natural in Ukrainian.

Yes, it is grammatical, but it is less neutral and less idiomatic in everyday speech.

For body parts and physical pain, Ukrainian usually prefers:

• У мене болить підшлункова залоза

Using моя can sound more emphatic, contrastive, or stylistically marked, as if you are stressing that it is my organ, not someone else’s.

So for a learner, the safest natural pattern is:

• У мене болить + body part

Because підшлункова залоза is singular.

The subject of the sentence is підшлункова залоза, so the verb must also be singular:

• підшлункова залоза болить = the pancreas hurts

If the thing that hurts is plural, then you use болять:

• У мене болять зуби = My teeth hurt
• У мене болять ноги = My legs hurt

So the pattern is:

• singular noun → болить
• plural noun → болять

• мене is in the genitive
• підшлункова залоза is in the nominative

Why?

1. У мене

After у/в in this kind of possession-state construction, Ukrainian uses the genitive:

• я → мене
• ти → тебе
• він → нього
• вона → неї

2. підшлункова залоза

This is the thing that is doing the hurting grammatically, so it stays in the nominative:

• підшлункова залоза болить

In Ukrainian, with боліти, the thing that hurts is usually treated as the subject.

So Ukrainian thinks more like:

• The pancreas hurts at me

That is why підшлункова залоза is nominative and the verb agrees with it.

This is the same pattern in many common sentences:

• У мене болить голова
• У мене болить живіт
• У мене болять руки

Even though English uses a possessive idea, Ukrainian often uses this subject-based structure.

Yes. У and в often alternate in Ukrainian for euphony, and here they mean the same thing.

So both are possible:

• У мене болить підшлункова залоза
• В мене болить підшлункова залоза

In careful writing, speakers often choose whichever sounds smoother next to the surrounding words. In everyday speech, both are common.

Yes, absolutely. That is very common.

In everyday speech, Ukrainians often shorten medical terms when the meaning is obvious:

• підшлункова залоза → підшлункова

So:

• У мене болить підшлункова

sounds natural and is probably more colloquial than the full version.

The full form підшлункова залоза sounds more complete, technical, or medical.

It is a compound medical term.

• залоза = gland
• підшлункова is related to під шлунком, meaning under the stomach

So literally it is something like:

• the under-the-stomach gland

That is the Ukrainian term for the pancreas.

They are related, but they are used differently.

болить

Use this when a specific thing hurts:

• У мене болить підшлункова залоза
• У мене болить горло

боляче

This means it hurts or it is painful, and it often focuses more on the feeling than on a grammatical subject:

• Мені боляче = I am in pain / It hurts
• Мені боляче ковтати = It hurts to swallow

So here болить is the right choice because you are naming the thing that hurts.

No, Ukrainian word order is fairly flexible, but the version you have is the most neutral and natural.

Neutral word order:

• У мене болить підшлункова залоза

Other orders are possible, but they change the emphasis:

• Підшлункова залоза у мене болить → stronger focus on the organ
• Болить у мене підшлункова залоза → marked, context-dependent

For learners, it is best to stick with:

• У мене болить + body part

Also, у мене usually stays together as a unit.

A very useful model is:

• У + person in genitive + болить/болять + body part

Examples:

• У мене болить голова = My head hurts
• У тебе болить живіт = Your stomach hurts
• У нього болить спина = His back hurts
• У неї болять ноги = Her legs hurt
• У нас болить горло = Our throat hurts
• У них болять зуби = Their teeth hurt

So the sentence you have is part of a very productive everyday pattern.

It can work in normal speech, but the full phrase підшлункова залоза sounds a bit more medical or explicit.

In everyday conversation, many speakers would more naturally say:

• У мене болить підшлункова

That shorter form is common and natural. The full version may sound more like:

• speaking carefully
• speaking to a doctor
• using more formal or precise language

So both are correct, but they have slightly different style levels.