Most women under 25 don't need much. Three things are worth ruling out, though, and all three are cheap to check.

Why Bother Before 25?

Iron is the big one. Between monthly periods and a diet that's usually low on absorbable iron, stores drain slowly and quietly. You end up winded on the stairs, your hair thins, you can't concentrate, and you put all of it down to studying late or a bad week of sleep. It's rarely a bad week of sleep.

Thyroid problems often start in this decade too, and they mess with periods, weight and mood at the same time. Vitamin D is almost a given if you're indoors all day. None of these three announce themselves, and none of them are hard to fix once you know. That's the whole argument for testing now rather than at 35.

Who Should Consider These Tests

• Your periods are irregular, very heavy, or have stopped

• You're tired even after a full night's sleep

• Your hair's falling more than it used to

• You're vegetarian, or you eat on the run

• You barely see daylight on a working day

• You've never had bloodwork done and want a starting point

What Each Test Tells You

This page lists 7 options. Here's what each one actually measures, so you can pick instead of guessing.

Blood tests

• Complete Blood Picture (CBP): Counts your red cells, white cells and platelets. It's the cheapest way to catch anaemia or an infection you didn't know you had, and it's the single most booked test we do.

• Liver Function Test (LFT): Your liver handles everything you eat, drink and swallow. It puts up with a lot before it complains, so this picks up fatty liver or alcohol strain years before you'd feel anything.

• Thyroid Function Tests: Checks the hormones that set how fast your body runs. Worth doing if you're tired, gaining or losing weight without trying, or your hair's thinning.

• Ferritin Test: This is your iron savings account, and it empties before your blood count changes. That's why you can feel exhausted while a routine CBP looks perfectly fine.

• Vitamin D (25 - Hydroxy Vitamin D, Serum): Your body makes this from sunlight, and most people who work indoors don't get enough. Low levels show up as aching bones, weak muscles and flat mood.

Scans

• Abdominal Ultrasound: Painless look at your liver, gallbladder, kidneys and pancreas. No radiation, and it takes about fifteen minutes.

• Anomaly Scan: The detailed mid-pregnancy scan that checks your baby's organs and growth in full.

How to Prepare

• No fasting: Complete Blood Picture (CBP), Vitamin D (25 - Hydroxy Vitamin D, Serum)

• Usually 6 to 8 hours fasting. Some scans want a full bladder: Abdominal Ultrasound

• Booked between 18 and 22 weeks: Anomaly Scan

• Morning sample is better: Ferritin Test

• Skip alcohol for 24 hours first: Liver Function Test (LFT)

• No fasting. Take your thyroid tablet after the sample, not before: Thyroid Function Tests

Tell the collection team everything you're taking, prescription or not. Plenty of supplements move these numbers, and without that context your report reads wrong.

How Often to Repeat

Once a year is plenty if nothing's wrong. Go sooner if the tiredness won't shift, your periods change noticeably, or you're losing weight without meaning to.

Understanding Your Results

One value outside the range usually means nothing. Dehydration, a cold last week, the time of day, all of it shifts numbers around. What matters is the shape of the whole report and how it compares to next year's. Take the full thing to a doctor rather than panicking at one red line.

These tests point at a diagnosis. They don't make one. Read your report with a doctor who knows your history and what you're currently taking.