Health Reference LibraryFerritin 35: is that OK, or still on the low side?
This entry is part of the Nutri Tailor Health Reference Library — cited research on supplements, nutrients and adjacent areas of health.
Summary
A ferritin of 35 µg/L is low-normal. It sits above the UK deficiency threshold of 30 µg/L, but below 50, the level at which NHS guidance excludes iron deficiency, and below 40, where diagnostic studies report 98 percent detection accuracy. Without symptoms and with a stable trend, evidence supports nothing beyond a reasonable diet. Where tiredness, hair shedding or heavy periods are present, iron has not been ruled out at this level, and guidance supports a food-first correction with a repeat test at around three months, aiming for a result above 50, which settles the question.
Free iron and ferritin result interpreter
Enter what you have. Your ferritin alone works; the other fields sharpen the reading. Nothing you enter leaves this device. Nothing is saved. No AI is used, only published UK guideline thresholds.
This tool gives educational interpretation of published evidence. It is not personal dosing advice and it does not diagnose. It knows nothing about your history, symptoms or other results. Interpreting your results over time, alongside everything else about you, is what Nutri365 does.
How it works
Ferritin is the protein that stores iron, and a result of 35 µg/L indicates a real but shallow reserve. Stores at this level comfortably support day-to-day red blood cell production, which is why most people at 35 feel well. Two questions remain open in research terms. The first is resilience, because a training block, a heavy menstrual cycle or an illness with poor appetite draws down a shallow reserve quickly. The second is measurement, because ferritin rises with inflammation, so a person with a raised CRP may show 35 while their underlying iron position is lower. This is why guidance supports reading ferritin alongside CRP where symptoms are present.
Timing
Timeframes at this level are relaxed. A three-month repeat test is appropriate where action was taken, and the next routine blood panel where it was not. Studies of repletion suggest movement from 35 toward 50 on food and modest supplementation is realistic within a quarter. Where the number does not rise despite genuine effort, that lack of response is itself information, and a GP conversation about absorption or ongoing loss is the next step.
Safety profile
Nothing about a result of 35 is alarming, and the standard cautions are unchanged rather than heightened. Bleeding signs, unexplained weight loss and persistent abdominal symptoms belong with a GP whatever the ferritin. Anyone with haemochromatosis in the family is advised not to supplement iron on a low-normal result without advice, because inherited iron overload can sit at ordinary-looking ferritin levels for years.
Special populations
In menstruating women, a result of 35 with light periods and no symptoms is comfortable, while the same number with heavy periods represents a reserve being drawn down, and last year's result usually shows which applies. In endurance athletes, sports research often works to higher ferritin comfort ranges than general practice, and studies have reported performance gains from repletion in this range. In pregnancy, iron demands rise sharply through the trimesters, so a booking result of 35 warrants dietary attention early. In men, a stable 35 is unremarkable, while a fall from a much higher previous result is a trend worth understanding with a GP.
Guideline positions
The thresholds bracketing this band are consistent across guidance. UK practice aligned with NICE confirms deficiency below 30 µg/L, which a result of 35 clears. NHS diagnostic guidance reports that results below 40 µg/L detect deficiency with 98 percent sensitivity and specificity, so the 31 to 39 range remains statistically uncertain. Above 50 µg/L, NHS guidance regards deficiency as excluded. The WHO threshold for healthy adults sits lower, at 15 µg/L. Taken together, a result of 35 is more likely normal than not, and only a result above 50 closes the question.
Practical framework
The evidence supports two paths. Where there are no symptoms and the trend is stable, diet is the whole plan. This means iron-rich foods through the week, vitamin C paired with plant sources, and tea or coffee kept away from iron-containing meals, with a repeat test at the next routine bloods. Where symptoms are present, the trend is downward, or monthly losses are significant, guidance supports running the dietary correction properly and considering a supplement such as [Iron & Vitamin C](/products/iron-vitamin-c) on alternate days, a pattern supported by absorption studies, with a repeat test at three months aiming for a result above 50. Athletes seeking performance sit in the second group. Where a raised CRP accompanied the result, both tests are worth repeating once well before drawing conclusions. The [repletion timeline](/apps/learn/iron-supplementation-timeline-symptom-resolution-ferritin-normalisation) sets out expected pace. For readers who decide on a supplement, Nutri Tailor stocks [Iron & Vitamin C](/products/iron-vitamin-c) in the UK. To check your own result against the UK ranges, the Nutri Tailor [free blood test result interpreter](/apps/learn/free-blood-test-result-interpreter) reads ferritin and the iron panel, vitamin D, B12 and folate.
Ferritin thresholds at a glance (UK, µg/L)
| Threshold | Meaning | Source |
|---|---|---|
| Below 15 | Iron deficiency in apparently healthy adults | WHO 2020 |
| Below 30 | Iron deficiency confirmed in UK practice (92% sensitivity, 98% specificity) | NICE CKS / NHS |
| Below 40 | Deficiency highly likely (98% sensitivity and specificity) | NHS guidance |
| Above 50 | Deficiency excluded, unless inflammation is present | NHS guidance |
| Below 70 with inflammation | Deficiency still possible when CRP is raised | WHO 2020 |
| Above 500 | Possible overload or other disease, needs clinical evaluation | WHO 2020 |
Sources
- 2020. WHO guideline on use of ferritin concentrations to assess iron status. World Health Organization.
- 2024. Iron deficiency guidelines. NHS Scotland Right Decisions.
- 2023. Ferritin interpretation, a guide for GPs. Royal United Hospitals NHS (NICE CKS aligned).