The line on the home test was faint, and it was only a few days after a missed period. Now you want a clearer answer than a line can give.
A blood test gives you a number, called hCG, but one number says little. Two numbers taken about 48 hours apart show which way the figure is heading, and that direction is what a doctor reads. You can book a quantitative hCG blood test at 117a Harley Street and walk in any day of the week.
What the first number tells you
hCG is the hormone a pregnancy starts making soon after implantation. Home tests look for it in urine and answer yes or no. A blood test measures how much is there.
Laboratories commonly read a result under 5 IU/L as not pregnant and over 25 IU/L as pregnant (Exeter Clinical Laboratory). Between the two is a grey area, which is the usual reason a doctor asks for a repeat.
A figure above 25 still says little about how the pregnancy is progressing. Early on, hCG varies widely from person to person, so a first number that looks low or high predicts little. That is why the second test matters.
"One hCG result doesn't tell you much. It's the second one, a couple of days later, that shows which way it's heading. I book the two together."
Dr Penny Sheehan, General Practitioner, GMC 6056535
Forty-eight hours later: the second number
In early pregnancy hCG usually rises fast, roughly doubling every two to three days. A repeat test two days after the first lets the doctor compare the two figures and see the pattern. This is why the second draw is taken about 48 hours later and not the next day or the next week.
What rising, flat and falling figures tell a doctor
- Rising. A steady climb fits an early pregnancy developing as expected.
- Flat. A figure that barely moves is a reason for the doctor to look more closely, usually with a scan.
- Falling. A fall tells a doctor the hormone level is dropping. The number cannot say why, so the doctor talks it through with you and decides what comes next.
Each pattern is a pointer for a doctor to follow up, never a verdict from the numbers alone. A doctor may sometimes ask for a progesterone test alongside hCG.
When a scan becomes the better test
Once a pregnancy is far enough along for an ultrasound to show something, a scan tells a doctor more than hCG can. Your doctor will say when that point has come. After that, the blood tests have done their job.
Severe one-sided tummy pain, shoulder-tip pain, fainting or heavy bleeding needs urgent care (A&E or 999), not a blood test.
Booking the pair
The quantitative hCG test is £79.38 plus the £50 blood draw, with the result in 1 day. A pair taken about 48 hours apart is two visits and so two draws, which comes to £258.76 for both.
We are walk-in seven days a week at 117a Harley Street, Monday to Friday 09:00 to 18:00 and Saturday and Sunday 10:00 to 14:00. If your first test falls on a Thursday or Friday, the repeat can happen at the weekend. Come back about two days after the first draw. Either visit works as a walk-in blood test. For the timing of results, see how long blood test results take.
If you would like a doctor to talk through both figures with you, a doctor review of your report is an extra £75.
Which hCG test to book
We list two hCG tests, and they answer different questions. For pregnancy, book the quantitative test priced above. hCG (Oncology), at £75, is a tumour marker that doctors use for a different purpose, so leave that one aside for a pregnancy question.
If your question is about your cycle rather than a pregnancy, the female hormone blood test looks at a different set of hormones.
Questions people ask
Is a blood test better than a urine test?
A urine test tells you whether hCG is present. A blood test gives the amount, and that amount is what lets a doctor compare two results. It can also pick up hCG slightly earlier than most home tests, and a doctor can advise on timing for your dates.
What else can raise hCG?
Occasionally, certain medicines and some medical conditions raise it outside pregnancy, which is one more reason a doctor interprets the result for you and not the number alone.
Do I need to fast?
No. You can eat and drink as normal before the test.
Ready to book your pair
Walk in on any day, or book online, and bring your home test result if you have it. Both visits are at 117a Harley Street, where we run private blood tests in London every day of the week.