Content table
If you’ve ever tracked your cycle or tried to understand your body’s fertility signs, you’ve probably come across terms like LH rise, LH surge, LH peak, and Peak Fertility. They sound similar—but they don’t mean the same thing.
And when you’re trying to conceive, those differences can make all the difference.
Understanding the timeline of your LH rise, LH peak, LH surge, and your Peak Fertility can help you time sex more effectively and reduce the stress that often comes with guessing your ovulation.
Let’s break it down in simple terms.
Key Takeaways
- LH surge marks a significant rise in luteinizing hormone from your baseline levels. Ovulation is expected to occur about 24-36 hours after your LH surge.
- LH rise, on the other hand, indicates a small increase in your LH levels from your baseline levels.
- LH peak is your highest LH level — ovulation usually occurs 8–20 hours later.
- Inito marks Peak Fertility when your LH levels start to increase from your baseline. This is when your chances of pregnancy are the highest in your cycle.
- Having sex during either your LH rise, your LH peak, or your LH surge can maximize your chances of conception.
What Is an LH Surge?
You’ve probably heard of the LH surge most commonly out of the three terms, so let’s go over what it actually means.
LH stands for Luteinizing Hormone, a key hormone in your menstrual cycle that triggers ovulation. Think of LH as your body’s ‘ovulation alarm’.
In the first part of your cycle, LH levels are low. But as you approach ovulation, they start to rise significantly—this is what’s called the LH surge. The surge signals your ovaries to release an egg, usually within the next 24 to 36 hours.
In other words, your LH surge is your body’s way of saying: “Get ready — ovulation is about to happen!”
The timing and pattern of this surge can differ from person to person (and even from cycle to cycle). Some women have a short, sharp spike; others have a slower, gradual rise that lasts a bit longer.
Know more: What Does a ‘Normal’ LH Level Look Like?
What Is an LH Rise vs. an LH Surge vs. an LH Peak?
The terms LH rise, LH surge, and LH peak can sound almost identical — and it’s easy to get confused.
But while they’re all part of the same process, each marks a different stage of your Luteinizing Hormone (LH) pattern leading up to ovulation.
Here’s how they differ and what each means for your fertility:
- LH rise: An LH rise is the first sign that ovulation is approaching. It’s a small increase from your baseline LH level — for example, from 1 mIU/mL to around 3 mIU/mL. This early shift shows your body is starting to prepare for ovulation.
Here’s an example of what an LH rise can look like –
- LH surge: The LH surge is when LH levels rise exponentially, often jumping from baseline levels to much higher concentrations, say from (around 1 mIU/mL to 25 mIU/mL). This exponential increase triggers ovulation, which typically occurs 24–36 hours later.
Here’s an example of what an LH surge could look like –
Note: Irrespective of whether you have an LH ‘rise’ or an LH ‘surge’, ovulation will occur approximately 24-36 hours later.
- LH peak: This is when LH levels reach their maximum concentration during the surge — for example, around 20 mIU/mL if your surge surged from 1 to 20. Ovulation is expected to follow about 8-20 hours later.
How Can I Tell the Difference Between an LH Rise and LH Surge?
As discussed an LH rise vs. LH surge simply refers to the extent of increase in LH levels from baseline levels. While there are no set threshold levels to differentiate between a “rise” vs. “surge”, let’s take a look at one user’s Inito chart to understand this better.
As shown above, the user experienced a slight increase in LH levels on cycle day (CD) 15, which can be described as an LH rise. Then, on CD 20, her LH levels increased much more significantly compared to her baseline — this is what we’d call an LH surge.
In all three instances, regardless of the actual LH values, what mattered most was that her LH levels rose noticeably from her personal baseline.
Research supports why fixed thresholds don’t work well. One study that tracked daily LH levels throughout an entire cycle found that ovulation can occur with LH values anywhere between 6.5 mIU/mL and 101 mIU/mL. This wide range is exactly why baseline-based interpretation is so important.
LH patterns can also look different from cycle to cycle.
One common variation is a biphasic LH surge, where LH increases on one day, dips the next, and then rises again.
In this chart, you can see LH slightly increasing on both CD 14 and CD 16, forming a biphasic pattern of LH rise.
And in some cases (as shown below), LH rises well above baseline levels on both CD 20 and CD 22—meaning each of these days qualifies as an LH surge.
Across all these examples, the principle stays the same: it’s the change from your personal baseline—not a fixed LH number—that determines whether you’re seeing an LH rise or an LH surge.
What Is Peak Fertility?
We’ve gone over the LH rise, surge, and peak — now let’s talk about what they lead up to: Peak Fertility.
Peak Fertility is the point in your cycle when your chances of getting pregnant are the highest — this is the time to have sex if you’re trying to conceive, as your body is preparing to release an egg.
Peak Fertility signals that ovulation is likely to occur within the next 24–36 hours. By marking Peak Fertility at the start of the LH rise or surge, Inito helps you make the most of your highest-chance days.
Think of it this way: The LH increase is what’s happening behind the scenes — the hormonal change that triggers ovulation — while Peak Fertility is the action stage you respond to. Having sex during this window maximizes your chances of conception.
Here’s a quick overview of each phase of your LH levels and Peak Fertility:
Phase | What It Means | When Ovulation Typically Occurs | Fertility Level |
LH Rise | Small increase in LH levels above baseline — your body is preparing to release an egg. | 24–36 hours after LH begins to rise | Peak |
LH Peak | LH reaches its highest point. | 8–20 hours after LH peak | Peak |
LH Surge | Exponential increase in LH levels above baseline | Within 24–36 hours after the surge begins | Peak |
Peak Fertility | Inito marks Peak Fertility when LH starts to increase above baseline levels, signaling ovulation is near. | 24–36 hours after Peak Fertility begins | Peak |
When’s the Best Time To Have Sex After an LH Surge vs. Peak Fertility?
Since sperm survives in your reproductive tract for about five days, the goal is to have sperm waiting when the egg is released — not the other way around. That’s why having sex during any of these phases gives you a strong chance of conception.
In fact, research shows that conception rates are highest when intercourse happens before ovulation, rather than on the day of ovulation itself.
So you don’t even need to wait until Peak Fertility or your LH peak to start trying — it’s best to begin as soon as your fertile window opens, when your estrogen starts to rise.
So what if you have more than one LH surge? In such cases, it’s best to have intercourse each day of your surge!
Know more: Differences Between High Fertility and Peak Fertility
Not sure when this is?
This is where the Inito Fertility Monitor can help you. Inito measures four key fertility hormones in urine – LH, E3G, and FSH help you pinpoint your fertile window and time sex with confidence, while PdG (urine metabolite of progesterone) confirms if ovulation actually happened.
Wrapping It Up
Your LH surge, LH rise, LH peak, and Peak Fertility are all connected — but not identical.
To recap:
- LH Surge: A sharp rise in your LH levels
- LH Rise: A small rise in your LH levels
- LH Peak: Peak of LH surge
- Peak Fertility: The time when your chances of conceiving are the highest in your cycle
When you understand your hormone patterns, you stop guessing and start planning with confidence.
