What it means
I need a doctor. 需要 is "to need."
When to use it
In an emergency, 医院 (hospital, yīyuàn) is the word to get you there. Big cities have international clinics with English-speaking staff.
What Chinese people actually say
Say this instead: 我有点不舒服，要去医院 (wǒ yǒu diǎn bù shūfu, yào qù yīyuàn)
Chinese speakers rarely announce "I need a doctor" out of nowhere. They describe the problem first: 我有点不舒服 (I'm feeling a bit unwell), then say what they want to do: 我要去医院看一下 (I want to get checked at the hospital). If it's urgent, 快叫救护车！ (call an ambulance!) is what people actually shout — the number is 120.
Examples
wǒ我xū需yào要yī医shēng生，qǐng请bāng帮bāng帮wǒ我。
I need a doctor, please help me.
wǒ我xū需yào要kàn看yī医shēng生。
I need to see a doctor.
fù附jìn近yǒu有yī医yuàn院ma吗？
Is there a hospital nearby?
The full set of survival phrases for greetings, dining, shopping, and getting around, each with audio.