Black Seed Oil and Hashimoto's: What the One Trial Measured
Search black seed oil and Hashimoto's and you will find something unusual for this category: a real randomised trial, in real patients, with real numbers. That is rare enough in the black seed literature to be worth taking seriously — and precisely because it exists, it is worth reading properly rather than through the summaries. Hashimoto's thyroiditis is an autoimmune disease, managed with levothyroxine and monitored by blood tests, and it is not a condition where an encouraging headline should change anything you do. This article reports what that trial was, what it measured, what it did not measure, and where an independent review placed it. We are not going to tell you black seed oil supports, balances or improves your thyroid, because the evidence does not let us.
For our own oil, see our cold-pressed Ethiopian black seed oil.
The Short Answer
- One randomised, double-blind, placebo-controlled trial has examined Nigella sativa in people with Hashimoto's thyroiditis: Farhangi and colleagues, BMC Complementary and Alternative Medicine, 2016, volume 16, article 471 (PMID 27852303). Forty patients completed it, twenty per arm, over eight weeks at a single centre in Iran.
- The intervention was 2 g per day of milled black seed powder in capsules — not black seed oil. Almost every summary online describes it as an oil study. It was not.
- Every participant was already taking levothyroxine, and their dose was deliberately held fixed from six weeks before the trial until the end. The trial therefore cannot tell you anything about medication requirements.
- It measured blood markers and body measurements: TSH, T3, T4, anti-thyroid peroxidase antibodies, VEGF, nesfatin-1, weight, BMI, waist and hip circumference. It measured no clinical outcomes at all — no symptoms, no fatigue, no quality of life.
- An independent systematic review of supplements in this exact population concluded that because Nigella sativa has been examined in only a single study, conclusions cannot be drawn (Kubiak et al., Antioxidants, 2023).
- Black seed has documented effects on fasting glucose, HbA1c and blood pressure in pooled trial data. If you take medicines for diabetes or blood pressure, that is a conversation for your doctor, not a footnote.
- Sidr & Stone publishes a specific, independently verified figure of 2.67% thymoquinone, tested per batch by Analytice, an ISO-accredited French laboratory — a measured number, not a slogan.
Hashimoto's in One Paragraph — and What Manages It
Hashimoto's thyroiditis is an organ-specific autoimmune condition in which the immune system targets the thyroid gland, and it is the most common cause of hypothyroidism. It is characterised by thyroid autoantibodies in the blood — most commonly anti-thyroid peroxidase (TPO-Ab) — and by gradual loss of thyroid function. It is diagnosed and monitored with blood tests, and it is managed medically with levothyroxine, a thyroid hormone replacement whose dose is titrated against those blood results.
That last sentence is the fixed point of this article. Levothyroxine dosing is a clinical decision made against measured bloods by someone qualified to make it. Nothing in the research below is a reason to change a dose, skip a dose, delay a test, or substitute anything for it. If you take one thing from this page, take that.
The Trial People Are Talking About
Mahdieh Abbasalizad Farhangi, Parvin Dehghan, Siroos Tajmiri and Mehran Mesgari Abbasi published "The effects of Nigella sativa on thyroid function, serum Vascular Endothelial Growth Factor (VEGF)-1, Nesfatin-1 and anthropometric features in patients with Hashimoto's thyroiditis: a randomized controlled trial" in BMC Complementary and Alternative Medicine in November 2016 (volume 16, article number 471, PMID 27852303). It is a genuine, well-described, double-blinded, placebo-controlled trial, and the authors report their methods with unusual clarity. Here is what it was.
| Design element | What the paper reports |
|---|---|
| Design | Double-blinded, placebo-controlled randomised trial; permuted-block randomisation by an investigator with no clinical involvement |
| Participants | Adults aged 20–50 with physician-diagnosed Hashimoto's, recruited from outpatient endocrinology clinics of Isfahan University of Medical Sciences — a single centre |
| Numbers | 100 screened, 47 randomised (23 intervention / 24 placebo), 40 completed — 20 per arm |
| Intervention | 2 g per day of milled Nigella sativa seed powder, as two 1 g capsules taken before lunch and dinner |
| Comparator | 2 g per day of starch, capsuled identically |
| Duration | 8 weeks |
| Background medication | All participants on levothyroxine, dose held stable from 6 weeks pre-trial to the end by protocol |
| Power calculation | Powered on serum TSH only; 14 participants calculated, inflated to 40 to allow for 30% drop-out |
| Withdrawals | 3 in the intervention arm left because of itching and nausea; 4 in the control arm declined to continue |
| Funding | Grant from Tabriz University of Medical Sciences (project 93173) |
| Registration | Iranian Registry of Clinical Trials, IRCT2015021719082N4 |
None of that is a criticism. It is a competently run small trial that reported its own limits. The problem is entirely in how it has been retold.
What the Trial Measured — and What It Did Not
The results, as the authors report them: in the Nigella sativa group, body weight, BMI, waist and hip circumference fell; serum TSH and anti-TPO antibody concentrations fell; serum T3 rose; and serum VEGF fell, at p = 0.02. Nesfatin-1 did not change. None of these changes occurred in the placebo group. Those are the findings, stated as measured.
What follows is the part that matters more, and that almost nobody reproduces.
| What the trial measured | What the trial did not measure or show |
|---|---|
| Blood markers: TSH, total T3, total T4, anti-TPO antibodies, VEGF, nesfatin-1 | Any clinical outcome — no symptom scores, no fatigue measure, no quality-of-life instrument, no functional endpoint |
| Body measurements: weight, BMI, waist and hip circumference, waist-to-hip ratio | Any effect on levothyroxine requirement — the dose was fixed by protocol, so this was not testable |
| Dietary intake, to rule out confounding by energy or antioxidant vitamins | Whether antibody or TSH changes persist, reverse, or matter — follow-up ended at 8 weeks |
| Effects of 2 g per day of milled seed powder | Anything about black seed oil, at any dose, in this population |
| Outcomes in 40 people at one centre in one country | Replication — no second trial in Hashimoto's patients has been published |
A marker moving is not the same as a person getting better. Anti-TPO antibody concentrations are a diagnostic and monitoring feature of Hashimoto's; a fall in them over eight weeks in twenty people is an interesting observation that generates a hypothesis. It is not evidence that anyone felt different, needed less medication, or had their disease altered.
What an Independent Review Concluded About This Evidence
You do not have to take our word for the caution. Kubiak, Szmidt, Kaluza, Zylka and Sicinska published a systematic review in Antioxidants (2023, volume 12, issue 10, article 1798, PMID 37891878; PROSPERO registration CRD42022365149) asking exactly the right question: do dietary supplements affect inflammation, oxidative stress, antioxidant status and thyroid parameters in adults with hypothyroidism or Hashimoto's? They identified nineteen randomised controlled trials and three non-randomised studies.
Their verdict on this plant is one sentence long and worth quoting in full: because supplements such as Nigella sativa have been examined "only in single studies, conclusions cannot be drawn". That is an independent, peer-reviewed, systematic-review-level assessment of precisely the evidence this article is about, and it is more conservative than anything you will read on a supplement page.
The broader picture is no more forgiving. Li and colleagues, in Frontiers in Nutrition (2023, volume 10, article 1107750, PMID 37057067), appraised twenty systematic reviews of Nigella sativa and graded 110 outcome indicators: five moderate certainty, seventeen low, and eighty-eight very low. Fifteen of the twenty reviews were themselves rated critically low on methodological quality. That is the honest ceiling on confidence for this plant, and it applies to us as much as to anyone.
The Detail Almost Every Summary Gets Wrong
Here is a thing we could quietly leave out, because leaving it out would help us sell an oil.
The Farhangi trial did not use oil. The paper describes seeds bought from a local market in Isfahan, milled in a grinder into a purified powder, and encapsulated at 1 g per capsule by a pharmaceutical company under Good Manufacturing Practice. Participants took two capsules a day. Anyone reading that trial and reaching for a bottle of cold-pressed oil is not reproducing what was tested.
This is not a pedantic distinction. It has been observed elsewhere in the black seed literature that preparation matters: in a meta-analysis of eleven randomised trials of Nigella sativa and blood pressure, Sahebkar and colleagues (Journal of Hypertension, 2016, volume 34, issue 11, pages 2127–2135) found the systolic reduction of 3.26 mmHg was driven by powdered preparations rather than oils. Whole milled seed and pressed oil are different products with different compositions, and trial results do not transfer freely between them. We sell an oil, and we are telling you the trial used powder.
Safety Matters More Here Than Usual
Two things make caution more than a formality for this particular reader.
First, black seed measurably affects things other medicines also affect. In a meta-analysis of fifty randomised trials, Hallajzadeh and colleagues (Phytotherapy Research, 2020, volume 34, issue 10, pages 2586–2608, PMID 32394508) found pooled reductions in fasting glucose of 15.18 mg/dL and in HbA1c of 0.45 percentage points, alongside reductions in total, LDL and VLDL cholesterol. Effects on CRP, TNF-α, total antioxidant capacity and malondialdehyde were not significant. The blood-pressure meta-analysis above found small systolic and diastolic reductions. If you take medication for blood glucose or blood pressure, those are real pharmacological overlaps to raise with your doctor.
Second, there is a specific interaction signal worth knowing. Wang and colleagues (Chemico-Biological Interactions, 2022, volume 365, article 110070, PMID 35921950) reported that thymoquinone inhibits the CYP2C9 pathway involved in warfarin metabolism. That work was done in vitro — in laboratory preparations, not in people — and an in-vitro finding does not establish that the same thing happens in a human body. It is a flag for a conversation, not a conclusion.
And in the Hashimoto's trial itself, three of twenty-three people in the intervention arm withdrew because of itching and nausea. That is a real, reported tolerability signal in a small group.
Nobody should alter or stop levothyroxine because of anything on this page. Thyroid disease needs a doctor and blood monitoring. If you want to add anything to your routine, the person who reads your TSH results is the person to ask first.
If You Are Buying Black Seed Oil, Buy a Verified One
If, having read all of that, you still want black seed oil in your life as a food supplement — and many people reasonably do — then the useful question is which bottle actually contains what its label implies.
Khaikin and colleagues, in Nutrients (2022, volume 14, issue 17, article 3501, PMID 36079759), measured thymoquinone by HPLC-UV in eleven commercial black seed products and found contents from 3.08 to 809.4 mg per 100 g. That is a more than two hundred–fold spread across products sold under similar descriptions. It also means that a dose used in a trial cannot be mapped onto a retail bottle: you cannot know what you are taking unless someone has measured it. For a fuller walkthrough, see our guide to choosing a high-quality black seed oil.
| What to check | Why it matters | Sidr & Stone |
|---|---|---|
| A stated thymoquinone figure | Measured thymoquinone spans 3.08 to 809.4 mg per 100 g across commercial products (Khaikin et al., 2022) | 2.67%, stated openly |
| Independent per-batch verification | Seed composition varies by harvest; a single historic test does not describe your bottle | Verified per batch by Analytice, an ISO-accredited French laboratory |
| Extraction method | Thymoquinone is heat-sensitive; industrial refining reaches 200–270°C | Cold-pressed below 40°C, unrefined |
| Ingredient list | Blends and carrier oils change what a serving actually delivers | 100% pure Nigella sativa seed oil, single ingredient |
| Packaging | Thymoquinone is degraded by light | Matte black UV-protective glass |
Why Sidr & Stone
We have just spent an article declining to make the claim that would sell this product hardest, and pointing out that the one trial people cite used a preparation we do not sell. That is the standard we hold ourselves to on our own numbers too.
- Independently verified 2.67% thymoquinone, per batch
- Tested by Analytice, an ISO-accredited French laboratory
- Organically grown Ethiopian highland Nigella sativa — chosen after a 36-supplier evaluation
- Cold-pressed below 40°C to protect the heat-sensitive thymoquinone
- 100% pure — single ingredient, nothing added
- Unrefined — preserves the oil's natural integrity
- Bottled in matte black UV-protective glass
- Halal certified
- 10% of profits to charity
- Fulfilment in the UK, EU, and US
We will not tell you Sidr & Stone is the strongest or the best — that would be the very kind of claim this article warns against. What we will say is that our thymoquinone figure is 2.67%, independently verified per batch, and the evidence is there to see.
Frequently Asked Questions
What does the research say about black seed oil and Hashimoto's?
One randomised, double-blind trial of 40 completers found that 2 g per day of milled black seed powder over eight weeks was associated with lower TSH and anti-TPO antibodies, higher T3, lower VEGF and lower body weight, with no change in the placebo group (Farhangi et al., 2016). It measured no clinical outcomes, used powder rather than oil, and has not been replicated.
Can you take black seed oil with levothyroxine?
There is no published interaction study between black seed and levothyroxine. In the Hashimoto's trial, participants stayed on levothyroxine at a fixed dose throughout. Levothyroxine absorption is known to be affected by food and by some supplements, which is why it is usually taken on an empty stomach — so timing and additions are a question for the doctor who monitors your bloods, not for a blog.
Does black seed oil reduce thyroid antibodies?
We do not claim that it does. One eight-week trial in twenty people reported lower anti-TPO concentrations in the intervention arm using milled seed powder. An independent systematic review of supplements in this population concluded that, because Nigella sativa has been examined in only a single study, no conclusion can be drawn (Kubiak et al., 2023).
Who should be careful with black seed oil?
Anyone taking medication for blood glucose or blood pressure, given the pooled effects on fasting glucose, HbA1c and blood pressure in randomised trials; anyone on warfarin, given an in-vitro signal on the CYP2C9 pathway; anyone pregnant or breastfeeding; and anyone with an autoimmune condition, who should raise it with their clinician first.
Was the trial done with oil or with seeds?
Seeds. The paper describes seeds milled into a purified powder and encapsulated at 1 g per capsule, taken twice daily. Summaries describing it as a black seed oil trial are inaccurate, and preparation is not a trivial detail — a blood-pressure meta-analysis found the effect favoured powdered preparations over oils.
How does Sidr & Stone differ from other black seed oils?
We publish a measured thymoquinone figure — 2.67%, verified per batch by Analytice, an ISO-accredited French laboratory — rather than an adjective. Given that measured thymoquinone across commercial products ranges from 3.08 to 809.4 mg per 100 g, a verified number is the only meaningful basis for comparison.
Where can I buy a black seed oil whose contents have been measured?
From producers who publish independent per-batch laboratory results and will show you the certificate. Ours is available from our own product page, with fulfilment in the UK, EU, and US. Our notes on edible black seed oil cover what to look for on a label.
Is black seed oil a medicine?
No. Black seed oil is a food supplement, not a medicine. It has a long traditional history and an interesting body of research around thymoquinone, and can be a worthwhile part of a healthy routine — but it does not cure diseases and is not a substitute for medical care. Be cautious of any black seed oil marketed with specific disease-cure claims.
Final Thoughts
There is a real trial here, and it deserves neither dismissal nor the treatment it usually gets. Forty people, eight weeks, one centre, milled seed powder, fixed levothyroxine doses, blood markers only, no replication — and an independent systematic review saying that a single study does not support a conclusion. Everything in that sentence is verifiable, and everything in it is more useful than a headline.
What would change the picture is not another blog post. It is a larger, longer, multi-centre trial measuring things patients can feel, in a preparation whose composition is actually known. Until that exists, the honest position is interest without belief.
Hashimoto's is managed with levothyroxine and monitored with blood tests, and that is where decisions about it belong. If you want black seed oil alongside that as a food supplement, choose one whose contents have been measured by someone independent. Our cold-pressed Ethiopian black seed oil — independently verified at 2.67% thymoquinone — is available now, with fulfilment in the UK, EU, and US.
Shop Sidr & Stone Cold-Pressed Ethiopian Black Seed Oil — Verified 2.67% Thymoquinone →
Disclaimer: This article describes published research on Nigella sativa as it stood at the time of writing; research findings may change, and readers should check current sources. Black seed oil is a food supplement, not a medicine, and is not a substitute for medical treatment of any condition. Hashimoto's thyroiditis is an autoimmune disease that requires diagnosis, treatment and blood monitoring by a qualified clinician. Nothing here is a reason to alter, delay or stop levothyroxine or any other prescribed medicine. For any health concern, consult a qualified medical professional.